Service Information And Instructions For Use Of 5P3600 Hydraulic Flow Meter{0650, 5050} Caterpillar

All Hydraulic Circuits

The 5P3600 Hydraulic Flow Meter is the replacement for the former 9S2000 Flow Meter. The 5P3600 Hydraulic Flow Meter is an important tool for troubleshooting hydraulic circuits. The serviceman can control hydraulic oil flow and pressure with accuracy from the operator's compartment of the machine.

Features (Characteristics) Of The 5P3600 Hydraulic Flow Meter

VALVE CONTROLLER: An electrically powered load valve in the flow meter circuit is remote controlled by the operator. At machine start-up, an automatic feature built into the flow meter takes away this operator control, to put the load valve in a pre-set position. After start-up is complete, the operator will again have control of the load valve after pushing IN the VALVE RESET.

POWER SUPPLY: The unit will operate from either positive or negative ground machines. Connect either power lead to ground and the other lead to the battery.

PRESSURE MEASUREMENT SYSTEM: Multilayer spiral wound pressure gauge element with excellent (very good) shock, overload and vibration characteristics. Flow "velocity fuse" on the flow block, limits leakage of hydraulic oil from a broken pressure gauge hose or coupling to 8 L/min. (2 GPM) flow rate, before closing.

CIRCUIT CARDS: All printed circuit cards plug in for easy replacement.

CALIBRATION: Access is through the end panel for all readouts except for pressure. Calibration references for the thermometer are built into the unit.

EXTERNAL (OUTSIDE) TEMPERATURE: When probes from the 9S9102 Thermistor Thermometer Group are used with the unit, remote temperature readings can be made.

PANEL METERS: Panel meters are made stronger and no adjustment is needed except for mechanical zero.

FLOW LOSS SCALE: Use this scale to show the percent of flow lost when pressure is put in the hydraulic circuits.

STORAGE: Storage space for all accessories and cables is in the cover of the control unit.

5P3600 Hydraulic Flow Meter Specifications

RANGE OF FLOW: L/min "A" scale: 25-190 L/min (7-50 gpm) L/min "B" scale: 25-750 L/min (7-200 gpm) Percent flow loss can be set from 75-750 L/min (20-200 gpm) full scale.

RANGE OF TACHOMETER: RPM "A" scale: 400-2500 RPM RPM "B" scale: 400-5000 RPM NOTE: 5P7360 Tachometer Generator must be driven at one-half engine speed.

RANGE OF THERMOMETER: Double indication scale: 0°-150°C; 32°-300°F

RANGE OF PRESSURE GAUGE: Double indication scale: 0-41.4 kPa x 1000; 0-6000 psi

ACCURACY OF ALL READOUTS: ± 2% of full scale from 0°-40°C. Small reduction in accuracy to 50° C.

TEMPERATURE OF HYDRAULIC OIL DURING OPERATION: 0°-105° C. continuous; 150° C. intermittent.

MAXIMUM PRESSURE FOR HYDRAULIC SYSTEM DURING OPERATION: 41400 kPa (6000 psi) continuous; [42750 kPa (6200 psi) pressure relief disk burst pressure].

RATED BACK PRESSURE OF LOAD VALVE: 41400 kPa (6000 psi)

PRESSURE AT WHICH PRESSURE RELIEF DISKS WILL RUPTURE (BREAK): 29600 kPa (4300 psi) or 42900 kPa (6200 psi). The 29600 kPa (4300 psi) disk is installed in all new 5P3600 Hydraulic Flow Meter Groups.

POWER NEEDED: 12V-29V DC from vehicle electrical system (12 or 24 Volt machines). 1 ampere maximum under load valve stall condition. 10.5 V-12V DC will cause a reduction of load valve performance.

TEMPERATURE RANGE OF AMBIENT AIR DURING OPERATION: 0°-50°C.

WEIGHT: Control Unit 13 kg (28.5 lbs.) Flow Block 8.4 kg (18.5 lbs.)

SIZE: Control Unit 420 x 267 x 210 mm (16.5" x 10.5" x 8.3") Flow Block 370 x 89 x 198 mm (14.6" x 3.5" x 7.8")

Components Of The 5P3600 Hydraulic Flow Meter

A description of the components of the 5P3600 Hydraulic Flow Meter is as follows:

(1) Control Unit

(2) 6V7002 Temperature and RPM Meter ^*

(3) 6V7001 L/min Meter ^**

(4) Flow Block [Flow Block has a 0.25 mm (.010") 29600 kPa (4300 psi) Pressure Relief Disk inside]

(5) 5P7362 Cable Assembly for Tachometer

(6) 5P7360 Tachometer Generator (5P1759 Tachometer Drive Group, an optional tool, not shown, can also be used.)

(7) 6V4817 Hose Assembly for Pressure Gauge

(8) 5P7366 Power Cable Assembly

(9) 7N4153 Lamp (#1408 - also has two extra)

(10) 7N4154 Lamp (#45 - also has two extra)

(11) 5P7365 Cable Assembly for Flow Block

(12) 1P7411 Pressure Relief Disk [0.33 mm (.013") 42900 kPa (6200) - also has two extra]

(13) 6V4868 Pressure Relief Diverter Assembly (not shown)

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^*6V7002 is a metric meter. The 5P7372 Meter (English measurement) is still available for earlier flow meters.

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^**6V7001 is a metric meter. The 5P7368 Meter (English measurement) is still available for earlier flow meters.

Controls And Connections

1 PRESSURE GAUGE Gives hydraulic pressure of system that is tested.

2 AUX. - °C INPUT JACK Connection for cable and temperature probe from 9S9102 Thermistor Thermometer Group. Temperature scale on (6) gives probe temperature instead of oil temperature in the flow block.

3 RPM - °C SWITCH Gives either the temperature or RPM scale on meter (6). A temperature indication also serves as a power indication when there is a connection of power to the control unit.

4 RPM INPUT JACK Takes the input from the 5P7360 Tach Generator only. DO NOT USE THE NONCURRENT 9S3047 TACH GENERATOR WITH THE 5P3600 FLOW METER.

5 RPM A-B Gives the A or B scale on RPM meter (6).

6 RPM - TEMPERATURE METER Gives the RPM on A or B scale and temperature in °C.

7 L/min METER Meter gives L/min and % of flow loss.

8 PRESSURE GAUGE INPUT Gives a fast connect and disconnect fitting to the pressure gauge. Gives a check of system pressure through the 6V4817 Hose Assembly from the flow block.

9 PERCENT ADJUST Gives adjustment of % Flow Loss Scale to zero, under "Base Flow Rate" conditions.

10 A, B, % Gives a selection of these three scale ranges on L/min meter (7).

11 POWER CONNECTION Location to make a connection of 12-29V DC power.

12 CONTROL CONNECTION Permits the control unit to control and check the action of the flow block, through the 5P7365 Hose Assembly.

13 CAUTION LAMP Lamp flashes (goes on and off) when the load valve is more than 75% closed.

14 STALL LAMP Light comes on when the load valve is completely closed or when the motor is stalled (stopped).

15 VALVE CONTROL Gives remote control of load valve position in the flow block. When dial is at "10", or is all the way clockwise (CW), the load valve is closed. Counterclockwise (CCW), rotation of the dial will open the valve.

16 VALVE RESET Push down, then release this switch to let the VALVE CONTROL (15), command (control) the load valve after connection of the flow meter to a power source. Either of the two conditions that follow will cause the load valve to go into the reset position (load valve is 40% closed) and cause the valve control to lose command:

a) At the first connection of power to the control unit.

b) When the engine of the machine is shut down, after a test has been made.

This feature reduces the possibility of damage to the machine hydraulic system during engine start-up.

17 OUTPUT PORT OF FLOW BLOCK This port has a 1 5/8"-12 SAE straight thread that needs an O-ring to seal. Hydraulic oil from this port is sent to the hydraulic oil supply tank or the hydraulic oil filter.

18 PRESSURE RELIEF DISK Two pressure relief disks available - one for rupture pressure of 29600 kPa (4300 psi) and one for 42900 kPa (6200 psi).

19 INPUT PORT OF FLOW BLOCK This port has a 1 5/8"-12 SAE straight thread that needs an O-ring to seal. This port is also the input port from the vehicle hydraulic system.

Basic Tests Of Hydraulic Circuits With 5P3600 Hydraulic Flow Meter

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Be sure the load valve is open (caution light is not flashing) before any hydraulic oil flow is started through the flow meter. Injury to personnel and damage to the machine can be the result from too much pressure if the load valve is fully closed. Pressure relief disks made to rupture (break) [at approximately (9S6341) 29600 kPa (4300 psi) or (1P7411) 42900 kPa (6200 psi)] will relieve (let go) excessive (too much) pressure or pressure surges (rapid rise and fall of pressure) in the hydraulic system.

The flow block can be installed at any location in a hydraulic circuit. The inlet connection of the flow block has the identification mark "IN" and the outlet has "OUT". If possible, do not connect the "IN" port within 457 mm (18") of hydraulic valves because this can cause a problem with the accuracy of the flow measurement.

In-Line Hydraulic Circuit Connection

The illustration shows the components of a typical "in-line" circuit connection: (1) flow block, (2) implement control valve, (3) implement, (4) hydraulic oil pump, (5) supply tank for hydraulic oil.

The in-line, or series, connection of the flow meter into the hydraulic system measures flow and pressure in one part of the hydraulic system without any change in the performance of the hydraulic system. The in-line connection is normally used for the measurement of a constant oil flow, such as oil pump output or the rate of oil flow in a transmission oil circuit.

Tee Test Circuit Connection

The illustration shows the components of a typical "tee test" circuit connection: (1) flow block, (2) implement control valve, (3) implement, (4) hydraulic oil pump, (5) supply tank for hydraulic oil.

A "tee test", or parallel, circuit connection between the hydraulic oil pump and an implement control valve lets the mechanic troubleshoot the complete hydraulic system with this one connection. The "tee test" method is very good in the test of a hydraulic system that has more than one (multiple) circuit.

NOTE: When the flow meter is used in a parallel "tee test" circuit, be sure that the return oil line to the supply tank goes into the supply tank below tank oil level. If this is not done, the result will be foaming (air bubbles in the oil) of the oil in the supply tank.

Adjustment Of Mechanical Zero For Panel Meters

Before the start of a test or calibration, the pointer of each panel meter must be on zero "0". Put control unit (1) in a horizontal position as shown and disconnect the power.

Check the position of the pointer for each meter (2). If pointer adjustment is necessary, use a small screwdriver and turn the adjustment screw as shown, either clockwise or counterclockwise, to put the pointer exactly over the zero "0" on the left side of the scale.

Calibration Of Control Unit

Use a pulse generator, such as the 5P9698 Calibrator (1), to check the accuracy of the control unit. The calibrator releases a known number of pulses per second, which can be supplied (sent) to the meter circuits. Check the calibration of the control unit when a new panel meter is installed, or anytime there is a replacement of one of the printed circuit cards. Also, check calibration at least every six months.

(1) Remove the plate from the end opposite the handle on the control unit. Check the zero setting of the panel meters. See ADJUSTMENT OF MECHANICAL ZERO FOR PANEL METER.

(2) The 5P9698 Calibrator is needed as a signal source for the adjustment of L/min and RPM. NOTE: The signal source for temperature is inside the unit. DO NOT connect the from block to the control unit during the adjustment procedure.

(3) Connect the power cable to either a 12 or 24 Volt/DC power source.

(4) Adjustment of L/min (GPM): [the correct calibration is given on the serial number label (2) on the front panel].

a. Put the L/min (GPM) range switch (3) in the "A" position.

b. Install the calibrator cable in the L/min (GPM) CALIBRATION INPUT jack.

c. Turn the calibrator switch to 100 Hz. Adjust the L/min (GPM) "A" calibration potentiometer until the value on the L/min (GPM) meter "A" scale is the value shown on the serial number label for 100 Hz.

d. Put the L/min (GPM) range switch (3) in the "B" position.

e. Turn the calibrator switch to 400 Hz. Adjust the L/min (GPM) "B" calibration potentiometer until the value on the L/min (GPM) meter "B" scale is the value shown on the serial number label for 400 Hz.

(5) Adjustment of RPM:

a. Put the RPM-°C switch in the RPM position.

b. Put the RPM range switch in the "A" position.

c. Turn the calibrator switch to 400 Hz.

d. Fasten the 1/8" phone plug adapter to the calibrator cable. Install the plug in the RPM INPUT jack.

e. Adjust the RPM "A" calibration potentiometer until the value on the RPM meter "A" scale is 2400 RPM.

f. Put the RPM range switch in the "B" position.

g. Adjust the RPM "B" calibration potentiometer until the value on the RPM meter "B" scale is 2400 RPM.

(6) Adjustment of temperature:

a. Put the RPM-°C switch in the °C position.

b. Put the tip of a small screwdriver in the TEMP CALIBRATE switch and move it to the left position.

c. Adjust the 0°C calibration potentiometer until the value on the temperature meter is 0°C.

d. Move the TEMP CALIBRATE switch two positions (detents) to the right.

e. Adjust the 100°C potentiometer until the value on the temperature meter is 100°C.

f. Move the TEMP CALIBRATE switch back to the center position (detent).

Hook-Up (Connection) And Operation Procedure

Before the flow meter is put into operation, check the calibration and be sure that both meters are on zero. See CALIBRATION OF CONTROL UNIT and ADJUSTMENT OF MECHANICAL ZERO FOR PANEL METERS.

1. Install the flow block in the hydraulic circuit to be tested. See the Service Manual for TEE-TEST HOOK-UPS. Make sure of the flow block input and output ports.

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NOTICE
Be sure the diverter assembly is pointed away from the operator, and that the correct pressure relief disk is installed according to the machine that is to be tested.

2. Put the control unit in position at the operator's station. Connect the flow block and the control unit with the 5P7365 Flow Block Cable.

3. Install the 5P7360 Tachometer Generator on the engine. The tachometer circuit of the 5P3600 Flow Meter works correctly when connected to a one-half speed engine tachometer drive. Some Caterpillar engines have a tachometer drive on the engine, and others do not. For those engines that do not have a tachometer drive, see the TEE-TEST TOOL CHART for information on the use of the tachometer generator.

4. Connect the tachometer generator to the RPM INPUT jack on the panel of the control unit with the 5P7362 Tachometer Cable.

5. Connect the 5P7363 Pressure Gauge Hose between the flow block and the control unit. (Should this hose rupture (break) during operation, a "flow velocity fuse" on the flow block prevents more than just a squirt (small amount) of oil loss before the velocity fuse stops the flow.)

6. Connect the 5P7366 Power Cable to the control unit. Connect either of the battery clips to the frame of the machine. The other clip connects to either a 12 or 24 Volt DC power source. (If possible, always use 24 V.) Turn the machine disconnect switch to "ON".

7. The control unit must always be in a flat horizontal position before the panel meters are read.

8. Move the RPM and L/min (GPM) range switches to the "B" scale before engine start-up, to prevent meter damage from overrange.

9. DO NOT START THE ENGINE WITH THE "CAUTION" LAMP ON. In this condition the load valve is 75% or more closed and hydraulic system damage could be the result.

10. To check the CAUTION and STALL lamps - WITH ENGINE STOPPED:

a. Push the VALVE RESET button.

b. Turn the VALVE CONTROLLER knob to the fully closed "10" position.

c. The CAUTION lamp must flash as the valve gets to the 75% closed position.

d. The STALL lamp must light dimly when the valve is fully closed and is "stalled". (The STALL lamp is a fuse for the motor circuit. If this lamp does not come on, the motor will not operate until a new lamp is installed. If the STALL lamp goes out when the load valve is less than 75% closed, the CAUTION lamp will not light either as it should in step 10c.)

e. Open the load valve to at least "2" on the VALVE CONTROLLER before continuing. (Load valve reset position.)

11. NEVER push the VALVE RESET with the engine running unless the VALVE CONTROLLER is set between "0" and "5".

12. NEVER turn the VALVE CONTROLLER further closed than "5" unless the load valve has "caught up" with the VALVE CONTROLLER and the CAUTION lamp is flashing.

NOTE: If the VALVE CONTROLLER is adjusted too fast, the electric load valve must be given time to "catch up" with the "command" signal.

13. NEVER connect or disconnect the power cable, flow block cable, tachometer cable, or pressure gauge hose while the engine is running.

14. Temperature probes from the 9S9102 Thermistor Thermometer Group can be used with the control unit. To measure an external temperature, put the probe cable into the AUX °C INPUT jack on the front panel. This is a replacement for the temperature probe in the flow block with the external probe.

15. To measure FLOW LOSS (pump efficiencies, etc.) at any given base flow rate, turn the L/min (GPM) range knob to "%" and adjust the PERCENT ADJUST knob to 0 percent on the meter. Put a load on the hydraulic system to bring up the system pressure. Read the flow loss in percent directly on the flow loss scale. To measure actual L/min (GPM) flow, simply turn the L/min (GPM) range knob to the "A" or "B" scale.

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NOTICE
Keep the parts of the flow meter group together as a group. Do not use the control panel of one group with the flow block from another group because this can: (1) give test readings that are not correct, and (2) cause possible damage to the flow valve.

Replacement Of Pressure Relief Disk In Flow Block

(1) Remove 6V4868 Diverter Assembly (1) and retainer (2) for the pressure relief disk. Remove the ruptured (broken) disk.

(2) Install a new disk (3) and tighten retainer (2) to a torque of 35 N·m (25). If retainer (2) is tightened more than the specified torque, remove it and install a new disk.

NOTE: Tighten retainer (2) slowly because the specified torque is reached (found) quite soon.

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Do not tighten retainer (2) more than the specified torque. If the retainer is tightened too much, the disk can rupture at a pressure that is lower than its design pressure. If the disk does rupture, it is possible that hydraulic oil will be sprayed and cause injury to the service man.

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NOTICE
Always make sure that the correct pressure relief disk is installed. To test machines that have a relief valve pressure above 20700 kPa (3000), install a 1P7411 Pressure Relief Disk. To test machines that have a relief valve pressure below 20700 kPa (3000), install a 9S6341 Pressure Relief Disk.

General Troubleshooting And Repair Of The Flow Meter

Troubleshooting Of The Flow Meter Accessories

Check of 5P7366 Power Cable

(1) Use the 8S4627 Circuit Tester or an ohmmeter (1) and check for continuity of both conductors (wires).

(2) Check for short circuits between the conductors.

Check of 5P7365 Flow Block Cable

(1) The 5P7365 Cable has 14 conductors (wires), and these conductors are connected point-to-point ["A" on one connector is wired (connected) to "A" on the connector at the opposite end of the cable]. Use the 8S4627 Circuit Tester and check each conductor for point-to-point continuity.

(2) Check for short circuits from conductor-to-conductor. There must be no short circuits between any of the 14 conductors. If there are any short circuits, make a replacement of the cable assembly.

Check of 5P7362 Tachometer Cable

(1) Use the 8S4627 Circuit Tester or an ohmmeter (1) and check the tachometer cable for continuity of the center wire and the shield wire as shown.

(2) Be sure that there is not a short circuit between the shield and the center wire.

Check of 5P7360 Tachometer Generator Operation

A fast and easy check of tachometer generator operation is to connect one end of 5P7362 Cable (1) to 5P7360 Tachometer Generator (2). Connect the other end of cable (1) to RPM INPUT jack (A) on 5P3600 Flow Meter (3). Connect 12V or 24V DC to the 5P3600 Flow Meter. Turn RPM-°C switch to RPM and turn RPM-A-B switch to A. Turn the shaft of the tachometer generator, rapidly, by hand. If the meter shows any measurement at all, it is probable that the tachometer generator will operate correctly. If there is no indication of tachometer generator output, see CHECK OF 5P7360 TACHOMETER GENERATOR MAGNETIC TRANSDUCER.

Check of 5P7360 Tachometer Generator Magnetic Transducer

(1) Use an ohmmeter (1) to check the magnetic transducer and the lead for tachometer generator (2). The resistance reading for the magnetic transducer and the lead is 3800 ± 400 ohms.

(2) Be sure there is not a short circuit (reading of zero ohms on ohmmeter - light comes on if circuit tester is used) from the coil to the case of the tachometer generator. If there is a short circuit, make a replacement of the tachometer generator.

NOTE: The former 9S3047 Tachometer Generator had a short circuit from one side of the coil to the case. The new 5P7360 Tachometer Generator has a floating coil (no short circuit to the case).

At times, a static test (as given in steps 1 and 2) is not enough, and a dynamic test is necessary. See OUTPUT CHECK OF 5P7360 TACHOMETER GENERATOR.

Output Check of 5P7360 Tachometer Generator

(1) Connect the tachometer generator (1) to voltmeter (2). Use a small electric drill (3), as shown, to turn the tachometer generator. With this procedure, the reading on voltmeter (2) scale must be .5V to 1.5V AC at 1000 RPM.

(2) If the AC voltage output is too low, see ADJUSTMENT OF 5P7360 TACHOMETER GENERATOR.

Adjustment of 5P7360 Tachometer Generator

The distance from the magnetic transducer to the gear teeth on the drive shaft controls the output voltage of the tachometer generator. If the magnetic transducer is not near to the gear teeth, erratic (variable) readings will show on the tachometer at lower RPM of the engine. If the transducer is too far from the gear teeth of the drive shaft, no reading will show on the tachometer at any engine speed.

To adjust the output of tachometer generator (1), loosen locknut (2). Turn magnetic transducer (3) clockwise and at the same time turn drive shaft (4) by hand. You can feel several of the gear teeth on the drive shaft touch the end of the transducer when the adjustment is correct. Hold transducer (3) while locknut (2) is tightened. Turn drive shaft (4) to check the adjustment. The gear teeth must not touch the transducer after the locknut is tightened.

Control Unit

Adjustment of Load Valve Stall Point

The load valve must stall (completely closed position) and the stall lamp come on when the valve controller knob is between 8.70 and 9.00. This adjustment can be made only when the flow block is at ambient temperature [16°-27°C (60°-80°F)]. As valve components get warm from hot hydraulic oil, a correctly adjusted load valve will stall near 9.50. A correctly adjusted stall point will let the load valve close completely at any oil temperature below 104°C (220°F).

(1) To adjust the stall point of the load valve, remove the 12 screws (1) and carefully lift panel (2). Turn the valve controller knob to 8.85 and adjust R305 Stall Pot (3) until the stall lamp just comes on.

NOTE: Counterclockwise rotation of R305 Stall Pot will turn on the stall lamp; clockwise rotation of R305 Stall Pot will turn off the stall lamp.

(2) If the range of adjustment for R305 is not enough to let the load valve stall at 8.7 to 9.00 on the valve controller, see ADJUSTMENT OF FEEDBACK POTENTIOMETER.

NOTE: When panel (2) is put back in position, be sure the wire harness does not come into contact with R305 Stall Pot (3) and change the adjustment.

Replacement of Meter

(1) Remove the twelve screws (1). Lift panel (2) and put it in position on the right side edge as shown. Put marks on the wires at connections (A) as to their location, then disconnect the wires from the meter. Remove the four nuts (3) and remove the meter from panel (2).

NOTE: For the correct part number of a service replacement RPM - Temperature Meter and a L/min (GPM) meter, see the topic, "COMPONENTS OF THE 5P3600 HYDRAULIC FLOW METER" on page 6 of this instruction.

Replacement Of Circuit Card

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NOTICE
Circuits within the control unit can be damaged by voltage surges and static charges that can be released from service equipment or the human body. Do not remove circuit cards or do any service work on these assemblies until you thoroughly understand the following information.

General Information:

The readout circuit card and the valve controller circuit card have within them complimentary symmetry metal oxide semiconductor (CMOS) integrated circuits. These circuits have very high input impedances. On a dry day, the human body can have a static potential as high as several thousand volts. The high impedance input can not drain this high static potential without internal damage to the integrated circuits. Test equipment and soldering irons without a ground can release voltages which are different from the circuit card potential, often being one half of the AC line voltage. This would be far more than the 15 volt maximum voltage rating of the CMOS integrated circuits.

Circuit Card Removal and Installation

(1) Remove the twelve screws (1). Lift panel (2) carefully and put it in position on the right side edge.

(2) To be sure that you and the circuit are at the same electrical potential, touch a circuit ground point such as the AUX °C INPUT jack, RPM INPUT jack (on the front panel), or the heat sink on the valve controller card, as shown. The case of the control unit is not ground. Remove the two screws (3) that hold each circuit card in position.

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NOTICE
At time of installation, do not tighten screws (3) too tight. Tighten screws (3) until the screw head just touches the circuit card.

(3) Hold the circuit card edges at a point close to the connector as shown, and pull the circuit card out of the connector.

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NOTICE
If the circuit card is to be sent to Flo-Tech. Inc., immediately put aluminum foil all around it. Do not put the circuit card in plastic film or insulating type material.

Replacement circuit cards will be sent in aluminum foil. Do not remove the aluminum foil until you are ready to install the circuit card. First, put the aluminum foil in contact with the circuit ground of the control unit, remove the foil, hold the circuit card by the edges only and install the circuit card in position.

Service of The Circuit Cards

If available, connect a conductive bar, or an edge connector, with all contacts connected together to the circuit edge connections. Connect this bar or edge connector to ground, with a lead to the work bench or earth potential. Make sure that all test equipment and soldering equipment is at earth potential. Before hand contact with any part of the circuit, first put the hand to a ground on either the test equipment or work bench. Equipment for use in the service of CMOS circuitry is made in the United States by 3M Company and includes such items as conductive bars, conductive mats for work surfaces, wrist cuffs for grounding the serviceman, and conductive foam for handling and storage of integrated circuits. Emergency methods such as working upon damp rags has proved reliable, if the circuit is allowed to become throughly dry before installation.

To remove an integrated circuit, put a clip on each lead, then remove the solder and remove the leads one at a time. This will cause less damage to the circuit board. Do not remove the replacement integrated circuit from its conductive package or carrier until ready to install. After installation, remove the flux from the circuit with a solvent and let it become dry in still air. Do not use compressed air to make a circuit dry.

Additional information on service procedures for metal oxide semiconductors can be found in the data manuals from semiconductor manufacturers.

For parts that do not have a Caterpillar part number, write or call Flo-Tech, Inc. For flow meter repair service, return it prepaid to:

Flo-Tech, Inc.
403 South Washington Blvd.
Mundelein, IL 60060, USA
Phone: (312) 566-9120

When returning the Flow Meter to Flo-Tech, Inc. for repair, always give:

1. Description of the problem.

2. Where to send the unit after repair.

3. Name of person to whom the unit is to be returned.

4. Billing address, if it is different than the shipping address.

Flow Block

Stuck Load Valve

Some extraordinary (not normal) conditions can cause the load valve to "stick" or "freeze" (load valve will not move), cause the load valve motor to stall, and will not let the motor operate in either direction. Examples of such conditions are as follows: (A) Power is removed from the control unit, the load valve is closed and the flow block is hot. This will cause the load valve poppet to "freeze" when the flow block becomes cool. (B) A second condition is to close the valve under pressure to the STALL position, then release the pressure in the system being tested. This will sometimes cause the valve to stick. Usually all that is needed is to pressurize the system again and move the VALVE CONTROL of the control unit away from the stall position (open direction). This should free the load valve. To manually loosen a stuck load valve, use the procedure that follows.

Remove plastic plug (1) from the end of the motor cover. Use a 5/16" or larger screwdriver (2) as shown, and turn the lead screw of the valve stem counterclockwise (CCW), until the load valve is free. Because of motor and gear train drag (resistance) it is probable that much force will be needed to turn the lead screw.

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NOTICE
Never turn the lead screw clockwise (CW) for a stuck load valve; this can cause permanent damage to the valve poppet and the valve stem.

DC Resistance Check of Flow Block Circuit

Use an ohmmeter as shown above to check the pin-to-pin resistance as given in the chart. The values given are nominal. All circuits (each pin in the connector) must be isolated from the case (infinite resistance).

(1) Flow Meter Magnetic Transducer.

(2) Resistance is according to temperature as shown.

(3) Feedback Pot.

(4) Variable with the position of the load valve.

(5) Motor variable with the condition of the armature and brushes.

(6A) Ohmmeter X1 Scale (+ ohmmeter lead to B).

(6B) Diode.

(7A) Ohmmeter X1 Scale (- ohmmeter lead to B).

(7B) Open Circuit.

(8A) Ohmmeter X1 Scale (+ ohmmeter lead to B).

(8B) Diode.

(9A) Ohmmeter X1 Scale (- ohmmeter lead to B).

(9B) Open Circuit.

(10A) Ohmmeter X 10K Scale.

(10B) Open Circuit.

Removal of the Turbine Assembly

(1) Use 1P1857 Pliers (1) and remove retaining ring (2).

(2) Lift the end of flow block (3) and carefully slide turbine assembly (4) out of the flow block.

Disassembly of The Turbine Assembly and Service Procedure For The Turbine Assembly Bearing

NOTE: Do not disassemble the turbine unless it is necessary to install a new turbine bearing.

If the turbine in the flow block of the flow meter does not operate correctly, and the indication is that the problem is with the turbine bearing, first try to clean the bearing, before installation of a new bearing. The information that follows tells how to clean the bearing, and gives the correct replacement procedure, if bearing replacement is necessary.

The illustration above shows the turbine assembly in its assembled position. The parts that make up the turbine assembly are; (T) Inlet Straightening Section, (2) Spring, (3) Inlet Cone, (4) Retaining Ring (two needed), (5) Bearing, (6) Turbine, (7) Outlet Cone, (8) Shaft, (9) Outlet Straightening Section.

(1) Put the turbine assembly in a solvent such as alcohol, acetone or perchlorethylene to wash bearing (5) and turbine (6). After the solvent has evaporated (become dry and gone away), rotate (turn) turbine (6) on shaft (8) and check by ear for any bearing noise or drag (rough movement). The turbine must turn freely and come to a slow smooth stop without any sudden change of speed or sound.

(2) If the bearing runs smoothly after it has been cleaned, see INSTALLATION OF TURBINE ASSEMBLY. If the bearing does not run smoothly, go on to step 3.

(3) Hold inlet and outlet straightening sections (1) and (9), one in each hand, and carefully twist in opposite directions, to break loose one or both straightening sections from shaft (8). Remove the loose section(s). If both sections are removed go on to step 5.

(4) If outlet section (9) has not come off shaft (8), put the turbine assembly on a good support with the shaft in a vertical position, and lightly hit the end of the shaft with a soft brass hammer to loosen shaft (8) from inlet and outlet cones (3) and (7).

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NOTICE
To remove inlet cone (3) and outlet cone (7), hit straight down on the end of shaft (8) and be careful to not bend the shaft. If turbine (6) can be removed, do step 6, and if it cannot be removed, do step 5.

(5) If turbine (6) is still tight on shaft (8), put the shaft through a hole in a metal plate and let the outer diameter of the plate, around the hole, give support to the turbine. (The shaft is held in the inner race of the bearing in turbine (6) with a light press fit.) Use an arbor press, a drill press or a soft metal hammer to remove shaft (8) from the bearing race.

(6) Remove the two retaining rings (4) that hold bearing (5) in position. If bearing (5) will not come out of turbine (6), put the turbine on a flat metal plate and use a round metal rod and a hammer to push out the bearing. Do not use this bearing again.

(7) Wash all parts of the turbine assembly in a clean solvent. Put 6V1541 Quick Cure Primer on shaft (8), the bearing bore in turbine (6), the inner bore of each straightening section (1) and (9), and on the outside diameter (outer race) of the new ball bearing. Let the primer get dry for 3 to 5 minutes.

NOTE: Do not let the primer get on the bearing balls of the new bearing.

(8) Put 9S3263 Thread Lock in the center bore of inlet (long) cone (3). Put shaft (8) in the bore of cone (3) to get the thread lock the complete length of the bore in cone (3). Put shaft (8) through cone (3) to dimension (A) until the thread lock is dry. Dimension (A) is 8.7 (.343").

(9) Install one retaining ring (4) in turbine (6). Put a small amount of 9S3263 Thread Lock on the inside diameter of the bearing bore in the turbine and, install bearing (5) in the turbine, against the retaining ring.

NOTE: Use a clean tissue to remove any extra thread lock after the bearing is installed. Do not let any thread lock get on or near the balls of the bearing. Let the thread lock cure (become dry) for approximately 30 minutes. Check the bearing for a good free running (rotation) operation. If the free running operation is good, install the other retaining ring (4) in the turbine.

(10) Use a hollow tube [the same diameter as the inner race of bearing (5) in turbine (6)] and a press to install the turbine on shaft (8), so the inner race of the bearing is against the shoulder on inlet cone (3).

(11) Clean the shaft in solvent, then let it become dry. Put 6V1541 Quick Cure Primer on each end of the shaft. Be careful to not let the primer get on the bearing. Let the primer become dry.

(12) Install outlet cone (7) on shaft (8). Put 9S3263 Thread Lock on each end of shaft (8). Install spring (2), inlet straightening section (1) and outlet straightening section (9).

(13) Make reference to INSTALLATION OF TURBINE ASSEMBLY. Before the turbine assembly is put to use, let the thread lock cure for approximately 2 hours.

Installation Of Turbine Assembly

(1) At installation of the turbine assembly into flow block (1), turn the outlet straightening section just enough so fins (A) do not come into contact with the end of either the temperature probe or the magnetic transducer, on the inside of the flow block.

(2) Push the turbine assembly all the way in, to put into compression the spring inside inlet straightening section (2), then install retaining ring (3).

Adjustment Of Flow Meter Magnetic Transducer

Adjustment of the magnetic transducer is not normally needed unless it has been removed and again installed or unless new parts have been installed in the turbine. An incorrect adjustment will cause either erratic L/min (GPM) indication or no L/min (GPM) indication.

(1) Remove the six screws (1) and cover (2). Disconnect transducer wires (3), then remove transducer (4).

(2) Disassemble and inspect the magnetic transducer. Install new seals (5) if needed. Assemble the magnetic transducer and put jam nut (6) on the transducer as far as possible.

(3) Carefully install transducer (4) and seal washer (7) into the flow block.

(4) Use a flashlight (8) to see into the IN port of the flow block. Use an unsharpened (not sharp) lead pencil (9) to turn the turbine, and at the same time turn transducer (4) toward the turbine blades until the transducer just comes into contact with a turbine blade.

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NOTICE
Do not let the transducer put a force on the turbine blades because this will damage the turbine components and cause a loss of accuracy for the flow meter.

(5) Loosen transducer (4) 1/4 to 1/3 turn from the point of transducer-to-turbine blade contact. Hold the transducer in this position and tighten jam nut (6) as shown. After jam nut (6) is tight, check to see that the turbine turns freely.

Disassembly Of Load Valve And Valve Drive

(1) Remove six screws (1) and cover (2). Disconnect wires (3) for the temperature probe and wires (4) for the magnetic transducer. Remove six screws (5) and motor cover (6).

(2) Use a screwdriver as shown, and carefully close the valve. Remove two bolts (7) and two screws (8), then remove valve drive assembly (9). Do not turn valve drive coupling (10).

(3) Use a 5P3520 Spanner Wrench (11) to remove valve pilot assembly (12). Inspect seal (13) and backup washer (14). Make a replacement if necessary.

NOTE: Install all new seals in the flow block if the flow meter has been used with water-glycol systems.

(4) Remove valve stem (15). Inspect the seal and backup washer at location (A) in the end of the valve body. Make a replacement if necessary.

(5) Use 1F1153 Needle Nose Pliers (16) to hold poppet (17) at location (B), then pull out poppet (17).

(6) Inspect orifice (18) and drain hole (19) for foreign material. Inspect seal (20) and backup washer (21) and make a replacement if necessary. Check the outside diameter of the poppet for damage or wear.

(7) Use a 5/16" Screwdriver as shown, and carefully remove sleeve assembly (22) from the flow block.

(8) With sleeve assembly (22) removed, inspect seal (23) and the sleeve bore for damage.

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NOTICE
Be careful to not damage the bore.

Assembly Of Load Valve And Valve Drive

In the procedure that follows, always put clean hydraulic oil on all seals at the time of component installation into the flow block.

(1) Put lubrication on seal (1) and install sleeve assembly (2) into the flow block.

(2) Put lubrication on seal (3) and install poppet assembly (4) all the way into the valve seat in sleeve assembly (2).

(3) Put lubrication on the seals in valve body (5) and put a light grease type lubricant on the threads of valve stem (6). Do not use grease from a pressure type grease gun. Install (turn clockwise) valve stem (6) as far as possible in valve body (5), then loosen (turn counterclockwise) valve stem (6) three turns.

(4) Put lubricant on seals (7), and install and tighten valve body (5) in the flow block. Use 1F1153 Needle Nose Pliers (8) and carefully turn valve stem (6) clockwise so it is against poppet (4).

(5) If valve drive coupling (9) has not been turned, the drive slots (A) will be in alignment with the drive pin on valve stem (6).

NOTE: If drive slots (A) and the drive pin on valve stem (6) are not in alignment, see ADJUSTMENT OF FEEDBACK POTENTIOMETER. When the drive slots and drive pin are in alignment, go to step 6.

(6) After the valve drive is installed on the flow block, install all other parts on the flow block except for the motor cover.

NOTE: There must not be a bind (bad fit or connection) between the drive coupling and the valve stem. The bolt holes (for the bolts that fasten the valve drive assembly to the flow block) are large enough to give the small amount of valve drive assembly movement necessary to permit alignment of the valve drive assembly and the valve stem.

(7) Connect the control unit to the flow block with the flow block cable. Use the power cable and connect a 12V or 24V DC power source to the control unit. Turn the valve controller knob to 9.00. Push in the reset button. The stall lamp must come on between 8.70 and 9.00. If the stall lamp does not come on, see ADJUSTMENT OF LOAD VALVE STALL POINT. If the stall lamp does come on between the 8.70 and 9.00 range, install the motor cover.

Adjustment Of Feedback Potentiometer

Two conditions can cause the feedback potentiometer, R501, to need adjustment. These two conditions are:

1. The load valve was disassembled and, at assembly the slots on the valve drive coupling were not put in alignment with the drive pin of the valve stem.

2. The electrical components are old and the mechanical components of the flow meter are worn.

With the conditions as given above, the result is a load valve that cannot be adjusted to stall at 8.70 to 9.00 on the valve controller dial. Use the procedure that follows to adjust the feedback potentionmeter.

(1) Remove screw (1) and loosen screw (2).

(2) Turn potentiometer assembly (3) counterclockwise (direction of arrow) to disengage it from the drive gear on the gearbox shaft.

If alignment of the drive coupling and the drive pin in the valve stem was not possible before this time, turn the drive shaft of the gearbox with a screwdriver until the drive coupling is engaged with the drive pin in the valve stem. Install the bolts that fasten the drive assembly to the flow block.

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NOTICE
Rotation of the drive shaft of the gearbox before the feedback pot assembly is disengaged, can cause permanent damage to the feedback pot.

(3) Use a screwdriver and gently (slowly and carefully) turn valve drive stem (4) clockwise, to make sure the valve is closed and the valve stem is in the seat on the poppet. Carefully turn anti-backlash gear (5) of the feedback pot counterclockwise as far as it will go. Now turn it clockwise one-half turn.

NOTE: The direction of rotation given is for the view as seen from the motor end of the flow block.

(4) Hold the one-half turn position as given in step 3, and hold either gear segment [(6) or (7)] of anti-backlash gear (5) and turn the other gear segment, (6) or (7), a total of two gear teeth in either direction. Now turn the feedback pot assembly so the anti-backlash gear will engage the drive gear on the gearbox shaft. Install the screw that holds the feedback mounting bracket in position. Put a small amount of a light grease-type lubricant on the gears.

NOTE: One screw hole in the mounting bracket has a slot, so the mounting bracket can be moved for correct adjustment when the gears are engaged. Do not use force on the anti-backlash gear against the drive gears or the result will be, more than average wear on the bushing and shaft of the feedback pot.

(5) Adjust the valve stall point as given in ADJUSTMENT OF LOAD VALVE STALL POINT, then install the cover for the motor and the transducer.

Description Of Power Supply Circuit Card - Control Units With S/N 1M-18075M

Power input is through card edge connector pins V-U and T-S to the diode bridge made by D101 through D104. The diode bridge provides a correct power connection to the unit even if the polarity of the hookup is incorrect. Because of the forward voltage drop of the diodes, the output voltage of the diode bridge will always be approximately 1.2 Volts less than the input voltage.

A double section low pass filter is made by L101, C101, C102, and L102, C103, C104. This filter is necessary to prevent the transients that are present when the contacts of the starter motor solenoid on the vehicle engine open on startup. At one point in time, this voltage can be over 300 volts. Although C102 and C104 are only rated for 50 Volts D.C., the type of capacitor used has enough internal series resistance to prevent failure for the short time during the high voltage pulse. Do not use capacitors for C102 and C104 that are made by other manufacturers, because their internal series resistance value can be lower. Filtered power for the readout circuits, and the low level logic of the valve controller circuit is available at edge connector pins F, H, J, and K.

At input voltages above approximately 15V, REG101 keeps the voltage for the valve motor circuit at 12 volts, to prevent motor damage on 24V vehicle systems. During a period of current overload, REG101 will heat, which is sensed by its internal circuitry. The output voltage of REG101 will then "fold back" to a lower output voltage and cause a reduction in the output current. When the temperature of REG101 lowers, the output voltage of REG101 will increase to its former value. This device also has internal protection to limit its output current during a short circuit condition. At input voltages below approximately 15V, REG101 will not operate correctly and becomes an in-circuit series resistance, which causes a loss of valve motor torque.

To correct this problem, REG101 is electrically taken out of the circuit during lower voltages on the output of the filter section. REG102 is a voltage regulator that will keep output at 5 V with filter output voltages as low as 7 Volts. The output of REG102 is connected to the inverting input of voltage comparator 1C101. The noninverting input for 1C101 is connected to the junction of voltage divider R101 and R102. When the voltage from the filter falls below 14 Volts, the voltage at the noninverting input falls below 5 Volts, and causes the voltage on pin 7, 1C101 to go low which turns on PNP transistor Q101. D105 prevents the output terminal of REG101 from being driven more positive than its 12 Volt rated output as D105 is now in a non-conducting condition with its cathode more positive than its anode.

Troubleshooting The Power Supply Circuit Card - Control Units With S/N 1M-18075M

If there is a failure of any of the components in the power supply, C102 and C104 must also be checked. The troubleshooting chart that follows gives a problem and a probable cause. Check the components as listed. Install new components as replacements for those that check bad.

Voltage Test Points For Power Supply And Filter - Control Units With S/N 1M-18075M

Conditions of Test All circuit cards are installed in control unit, motor is not stalled and not running (not in operation) and the caution lamp is not flashing. Reference all voltages to edge connector terminals L, M, N, P and R except the input to the diode bridge. Check bridge output with both polarity input connections to be sure all diodes operate. Voltmeter at 20K ohms/V or higher. All voltages are DC Volts ± 10%. Voltages must be checked at both 12V and 24V input conditions, because the circuit operation is different between these two voltages.

Description Of Power Supply Circuit Card - Control Units With S/N 18076M-Up

Power input is through card edge connector pins V-U and T-S to the diode bridge made by D101 through D104. The diode bridge provides a correct power connection to the unit, even if the polarity of the hookup is incorrect. Because of the forward voltage drop of the diodes, the output voltage of the diode bridge will always be about 1.2 volts less than the input voltage.

An overvoltage detector and overvoltage switch is made by Z101, Q101, and Q102. Under normal operation, R103 biases the base of Q102 for it to be on and conduct current to the rest of the circuits. During cranking, or with the engine running, if the vehicle voltage regulator is shorted, circuit conditions or faults can generate large voltages that can damage the low voltage electronic circuits. If the input voltage to the flow meter is more than 33 volts, Z101 will conduct. This will cause the voltage at the connection of R101 and R102 to become more negative than the emitter of Q101, and Q101 will turn on. When Q101 turns on, it connects the base and emitter of Q102 together, which turns off Q102. R104 will make the turn off voltage of Q102 a little higher than the turn on voltage, so the circuit will not oscillate when it switches.

At input voltages above approximately 15V, REG102 keeps the voltage for the valve motor circuit at 12 Volts, to prevent motor damage on 24V vehicle systems. During a period of current overload, REG102 will heat, which is sensed by its internal circuitry. The output voltage of REG102 will then "fold back" to a lower output voltage, and cause a reduction in the output current. When the temperature of REG102 lowers, the output voltage of REG102 will increase to its former value. This device also has internal protection to limit its output current during a short circuit condition. At input voltages below approximately 15V, REG102 will not operate correctly, and becomes an in-circuit series resistance, which causes a loss of valve motor torque.

To correct this problem, REG102 is electrically taken out of the circuit during lower voltages (below approximately 15V) on the output of the overvoltage switch. REG101 is a voltage regulator that will keep output at 5 Volts with overvoltage switch outputs as low as 7 Volts. The output of REG101 is connected to the inverting input of voltage comparator IC101. The non-inverting input for IC101 is connected to the junction of voltage divider R105 and R106. When the output from the overvoltage switch falls below 14 Volts, the voltage at the non-inverting input falls below 5 Volts, and causes the voltage on pin 7, IC101, to go low, which turns on PNP transistor Q103. D105 prevents the output terminal of REG102 from being driven more positive than its 12 Volt rated output, as D105 is now in a non-conducting condition with its cathode more positive than its anode.

Troubleshooting The Power Supply Circuit Card - Control Units With S/N 18076M-Up

Voltage Test Points For Power Supply - Control Units With S/N 18076M-Up

CONDITIONS OF TEST: All Circuit cards are installed in control unit, motor is not stalled and not running (not in operation) and the caution lamp is not flashing.

Voltages were measured using the 6V3030 Digital Multimeter or equivalent volt meter.

Voltages are referenced to circuit common pins L through R, except as indicated.

Voltages are in DC Volts except as indicated.

Voltage spread shown is only typical and can be different from the values given.

Description Of Readout Circuit Card

Power input (12 or 24 Volts) is by way of circuit board edge pins B (positive input) and C (negative input); L201 and C211 make up a filter network. REG201 adjusts incoming power to +5V and C212 gives improved regulation to transients.

NOTE: Unless given differently, the following discussion is for RPM only, but also with application to similar components of the L/min circuit.

The input signal from the tachometer generator is by way of P.C. card edge pins 17 and 18. C201 filters high frequency noise pulses. C202 couples this signal to the input of the Schmitt Trigger Circuit, IC201A, pin 8.

R201, R204, and variable resistor R206 make up an adjustable bias network which adjusts the trigger sensitivity. Pin 10 of inverter IC201A (nor gate) drives input pins 5 and 6 of inverter IC201B. Pin 4 of IC201B sends regenerative (positive) feedback to pin 9 through R205. There are two settings of R206 which will give the needed sensitivity. Sensitivity increases between these points, and decreases beyond these points. One of these two settings will give greater noise immunity than the other, with less "ringing" or false triggering. This sensitivity setting must be found by the sensitivity adjustment procedure as it is not the same from one unit to another. See ADJUSTMENT OF RPM AND L/min SENSITIVITY.

C203 and R208 differentiate the negative going edge of the Schmitt Trigger Output. IC201C and IC201D form a monostable multivibrator whose time constant is controlled by C204 and R209 or R210 according to the RPM range selection on SW602. R209 and R210 are selected values due to differences from unit to unit in the switching transfer point of IC201. See REPLACEMENT OF IC201, IC203. R208 has a second purpose, to send regenerative feedback to the input of the monostable multivibrator.

The output of the monostable multivibrator is taken from pin 13, through R207, and drives Q201. The collector of Q201 drives the meter circuit through R211, SW603, SW602, the meter M601, and the appropriate calibration potentiometer on the calibration circuit card which connects back to +5V by way of edge connector pin 4 on the readout circuit card.

The L/min circuit has one additional range which is the continuously variable "percent flow loss" range. Control panel potentiometer R601 provides a variable time constant for the one shot multivibrator in place of A and B L/min range resistors, R224 and R223.

The RPM monostable has a second output through R212 which drives a "Missing Pulse Detector" circuit, IC202, Q202, and Q203. For every pulse out from the RPM circuit, timer IC202 is set with a negative going pulse from Q202. This starts an R-C timing sequence constrolled by R213 and C206. Simultaneously, Q203 resets C206 to about .6 Volts, so that each timing sequence starts from the same potential. The R-C time constant is set so that with normal engine speeds, the circuit will be reset before the voltage on C206 is permitted to increase to 3.33 volts. When the engine is shut off, the RPM rate eventually is slow enough to permit C206 to charge to 3.33V without being reset (about 150 RPM). This is detected by pin 6, IC202 which causes the output at pin 3, IC202 to go low. This output transition is sensed in the valve controller circuit, and causes the valve to run to its pre-determined safety position (40% closed).

The temperature circuit is based upon operational amplifiers IC204 and IC205. Since the power supply has only a single positive polarity output, it is necessary to bias the operational amplifiers to a linear operating point with the voltage divider made up by R227 and R231, which connects to the non-inverting inputs of IC204 and IC205. The thermistor temperature sensor SEN502 connects to the circuit from closed circuit jack J602 (AUX °C), and edge connector pin 6. Bias for the thermistor is provided by R226. Edge connector pin 5 connects to the calibration circuit where calibrating resistors R407 and R408 are introduced into the circuit by SW401 (see SCHEMATIC, CALIBRATION CIRCUIT CARD). IC204 changes the voltage output from the thermistor to the current needed to drive meter M601. The actual voltage gain is less than 1, with the gain being set by the ratio of R233 to R230. The output of IC204 connects to the positive side of M601 from SW603. The negative side of the meter returns to the circuit from SW603, and span calibration potentiometer R406. IC205 does not actively amplify any signal. Its purpose is to provide a circuit return point, with identical gain and drift characteristics to IC204. IC205 also sets the circuit zero point with the zero calibration potentiometer R405, from edge connector pin 2.

Troubleshooting The Readout Circuit Card

NOTE: Before troubleshooting the circuit, see if the normal calibration procedure for the circuit can be done.

Voltage Test Points For Readout Circuit Card

Conditions of Test: 24V DC input. No RPM or L/min input. Flow block at 25°C or 30K ohm ± 1% resistor used in place of temperature sensor. Voltmeter 20K ohm/V or higher. Measure regulator voltages first. All voltages ± 10% x regulator error. Reference voltages to card edge Connector Pins C, D, E or F.

Reg 101: Input 22.5V, Output 5.0 ± .2V.

Use Of An Oscilloscope To Troubleshoot The Readout Circuit Card

All waveforms are taken with the flow block disconnected, 24V DC power and a 5P9698 Calibrator as the signal source.

To test the RPM circuits, connect the 5P9698 Calibrator into the RPM input jack, and for L/min circuits, connect the calibrator into the L/min. calibration jack on the side of the control unit.

The information that follows is for all Readout Circuit Card oscillograms.

1) 5P9698 Calibrator output frequency at 400 Hz.

2) If the bottom of each waveform is not at zero Volts, an additional single, straight trace is the zero indication.

3) Signal ground is taken from card edge pins C, D, E or F.

4) Oscilloscope sweep at 1 millisecond/D1V.

5) Oscilloscope vertical sensitivity at 1V/D1V, except where differently shown.

6) RPM range switch at A scale.

7) RPM -°C switch on RPM.

(1) IC201A or IC203A, pin 8, vertical sensitivity at 0.5V/Div. TP-1A, RPM-TP-1B, L/min.

(2) IC201A or IC203A, pin 4. TP-2A, RPM-TP-2B, L/min.

(3) IC201A or IC203A, pin 11. TP-3A, RPM-TP-3B, L/min.

(4) IC201A or IC203A, Pin 13. TP-4A, RPM-TP4B, L/min.

(5) Q201 or Q204, Collector. TP-5A, RPM-TP-5B, L/min.

(6) IC202, Pin 6. Vertical sensitivity at 0.2 V/Div. TP-6.

Replacement Of IC201 And IC203

The information that follows makes reference to the RPM circuit IC201 only, but this information is also good for the L/min circuit IC203.

When there is a replacement of IC201, it is possible that R209 and R210 will need different values of resistance. After a replacement of IC201, if the RPM calibration pots A scale (R403) and B scale (R404) do not have enough range to again calibrate (see CALIBRATION OF CONTROL UNIT) the readout, then R209 and R210 must be hand picked as follows:

Adjust both calibration pots, A scale and B scale, to the center of their mechanical rotation. Remove R209 and R210 from the readout circuit card. Make a selection of resistors, with values near those that were removed, until each range, A and B, reads near the calibration values given on the serial number plate of the unit.

NOTE: If the original values of R209 (B scale) and R210 (A scale) cause the RPM readout to calibrate too high, or above the desired values, the resistance of R209 and R210 is too great. (On L/min circuit, R223 is A scale and R224 is B scale.) Decrease in 500 ohm steps until correct calibration is within the range of the calibration pots.

Adjustment Of RPM And GPM Sensitivity

This adjustment procedure will probably not be needed unless there is a replacement of IC201 or IC203.

(1) Check RPM and L/min calibration and make adjustments as necessary. See CALIBRATION OF CONTROL UNIT.

Equipment needed for adjustment of RPM and L/min Schmitt Trigger sensitivity is: (1) Sine Wave Generator; (2) AC Voltmeter [if AC Voltmeter is not available, use an oscilloscope and adjust trigger point to 354 mV P-P (125 mV RMS)]; (3) connection to RPM input jack and L/min calibration input jack (use only one at a time).

Sensitivity Curve of RPM and L/min Schmitt Trigger circuits.

A. Lower sensitivity trigger point.

B. Upper sensitivity trigger point.

C. Potentiometer range where meter indicates.

4. Counterclockwise end of pot rotation.

5. Clockwise end of pot rotation.

6. Degree rotation of sensitivity adjustment pot.

7. Schmitt Trigger sensitivity in rms Millivolts.

(2) Connect the test circuit to the RPM input, and then to the L/min calibration input as shown in Figure 1.

(3) Turn RPM Sensitivity Pot R206 (8), or L/min Sensitivity Pot R220 (9), through its range. There must be an indication (reading) on the RPM or L/min meter only when R206 or R220 is near the center of its rotation, and must show no indication at either end of the rotation. See the illustration that shows the Sensitivity Curve of RPM and L/min Schmitt Trigger Circuits.

(4) Adjust the sensitivity potentiometer so the meter indication or trigger becomes marginal (lower limit of acceptability), see point A. Vary (change) generator output level up and down, and take note of the voltage needed for no indication on the meter, and the voltage needed for a steady indication on the meter. See also, if at any time the meter indication becomes erratic and "kicks up scale".

(5) Again adjust the sensitivity potentiometer to point B, and look for the trigger differential and any erratic (variable) movement.

(6) Make a comparison of the results from steps 4 and 5. Again adjust the sensitivity potentiometer, if necessary, to the set point, either A or B, with the least erratic movement and the least differential voltage input between no indication on the meter, and a steady indication on the meter. A good Schmitt Trigger will have a differential "noise band" voltage of 2 to 5 millivolts.

Description Of Valve Controller Circuit Card

See the schematic for VALVE CONTROLLER CIRCUIT CARD

Power input (12 or 24 Volts) is by way of edge pins 17 (negative input) and 18 (positive input) with L301 and C309 making a filter network. REG301 keeps incoming power at +8 Volts and C311 gives improved regulation to transients.

A voltage divider made up of R305 Command Potentiometer R602, and R307 provide the valve control input signal from edge pin 6, to pin 4 of IC303. The adjustment of R305 controls where on the VALVE CONTROLLER knob that the valve motor stalls, and R307 makes sure that no command voltage is possible that would cause the valve to open too far and drive the feedback potentiometer, R501, into its mechanical stop. IC303 is an integrated circuit connected as an analog switch. This switch is controlled from pin 6 of IC302B which is the output of a negative set R-S flip flop. A high output level on pin 6 will cause the analog switch to be connected to the "command" potentiometer (valve controller knob) voltage divider. A low output level on Pin 6 will connect the analog switch to the reset voltage divider formed by R303 and R304. This establishes the voltage for the preset valve reset position.

The negative set R-S flip-flop, IC302, has its logic state determined from three different sources. (1) When power is first turned on, C302 remains at a 0 logic level and pulls down pin 1 from D301. C302 then charges to +8V from R308, changing D301 to a non-conductive state. This will set pin 6 initially at logic zero. (2) If engine speed falls below 150 rpm, (25 Hz) IC202 on the Readout Circuit Card has a negative going output transition which is coupled to pin 1 of IC302 from edge pin 4, and the interface circuit formed by IC301A, IC301B, and C301. This condition also sets pin 6 of IC302B to a logic zero. (3) Resetting the R-S flip-flop from the valve reset position to the normal operating mode of pin 6 at a high logic level is done by connecting pin 5, IC302B to ground potential from edge pins 3 and 11 with SW604.

The output voltage from IC303 is connected to R313 which does a current conversion for pin 13 or IC304B. IC304 is a current input Norton amplifier being used as a voltage comparator. This current input is compared to the voltage brought in from edge pin 9 from the feedback potentiometer R501, and is converted into a current for pin 8 by R312. R312 value equals R313 value, so equal voltages will result in equal currents. If the input current at pin 8 is greater than pin 13, the output voltage at pin 9 will be low. C304 and C305 are needed to prevent oscillations in this stage when the currents to pins 8 and 13 are equal. This condition occurs when the motor (and feedback potentiometer) has reached the desired position. At this time the voltage at pin 9 will be at one-half of the +8V supply voltage. This can also result in oscillation and indeterminant logic states in the down stream digital logic.

The above described indeterminant conditions are eliminated by voltage comparators IC304C and IC304D. These comparators have input resistances which are unequal so that unequal voltages are needed to yield equal currents. When the current through R315 is greater than R316, the logic condition at pin 4 is low, when the current through R318 is greater than R319, the logic condition at pin 5 is low. This logic condition is sensed by pins 8 and 9 of IC306A which act as a negative logic AND gate, resulting in a logic 1 on pin 10 only when pins 8 and 9 are both low. (Motor at desired position.) Pin 10 is connected to pins 2 of IC306B, and 12 of IC306C which are also used as negative logic AND gates. Anytime a logic 1 appears on pins 2 and 12, a logic 0 will appear on pins 1 of IC306B and 13 of IC306C, no matter what the logic level is on pins 3 and 11. This results in the motor not getting power anytime the voltage on pin 9 of IC304B is greater than 1.0V or less than 7.5V. The 'deadband' between 1.0 and 7.5V not only prevents difficulties due to indeterminant logic states, but also prevents overshoot and 'hunting' of the motor when the proper valve position has been reached.

When the output voltage on pin 9, IC304B, is less than 1.0V, a logic 0 will appear at both pins 11 and 12 of IC306C, resulting in a logic 1 at pin 13. This turns on the Darlington connected transistor pair Q304 and Q305 which provide the base drive current to saturate Q307 and Q308. Approximately .3 volts appear on edge pin 2, and 11 volts on edge pin 16, (voltage reference is edge pins S and T) resulting in the valve motor turning the valve open. This is the only control mode to open the valve and is always a 100% duty cycle on the motor. The possibility of a logic 1 appearing at pin 11, IC305D, is eliminated by a logic zero also appearing on pin 13, IC305D, which results in a logic 1 on pin 3, IC306B preventing a "close" command while the valve is opening.

To operate the valve motor in a closing direction, three different duty cycles are used; 33%, 66%, and 100%. The 100% is used only when the valve motor (valve stem) is more than two turns (more than 1/4open) away from the 'stall' condition, the 66% when less than two turns, and the 33% for a period of 1/2sec. every time the motor reverses from running open to running close. The 33% duty cycle is additional insurance that the controller seeks a proper 'deadband' null without 'hunting.'

The two-turn valve stem position is determined by the currents flowing through unequal resistors R310 and R311 into pins 11 and 12 of IC304A. When the current in R311 becomes greater than R310, the output at pin 10 goes high (the feedback pot voltage at edge pin 9 will be near 6.16 volts.) This enables the 'caution' flashing lamp by inverting to a low through IC301 inverter pins 9 and 8, which turns off Q301, and allows C310 on astable multivibrator IC307 to charge to its normal levels.

For 100% duty cycle with valve closing, the output at pin 9 of IC304A must be high. This will disable the 'deadband' comparators, and the output of pin 10 IC306A, will go low. Since pin 11 of IC306C has gone high, no output appears at pin 13, IC306C. Instead, the output of pin 9 of IC304B being high, causes the negative logic OR gate pins 12 and 13, IC305D, to go low on its output pin 11, as pin 12 input is at high logic level for 100% duty cycle. This turns on Darlington pair Q302 and Q303 which saturates Q306 and Q309, applying 11 volts to edge pin 2 and .3 volts to edge pin 16. (Voltage reference is edge pins S and T.)

For 66% duty cycle (valve more than 3/4 closed) pin 9 of IC304B is high and pin 10 of IC304A is high, causing the output of NAND gate pin 8, IC302C to go low. This causes the output at pin 11, IC302D to go high as its other input, pin 13, is normally at a high state. The high output from pin 11, IC302D, and the alternating logic level from the multivibrator output pin 6, IC301E, combine in the negative logic OR gate pins 9 and 10, IC305B, causing the output pin 8 to alternate in logic state. This alternately enables and disables pin 12, IC305D, causing the motor to be powered 66% of the time. The output at pin 6 of IC301E at this time is high only 33% of the time, but goes through three inversion processes between pin 6, IC301E and pin 1, IC306B so the entire net signal is inverted resulting in a 66% duty cycle of power applied to the motor.

For 33% duty cycle, the duration is only one-half second, and occurs when the motor switches from "valve open" to "valve close" and frequently when the valve is commanded to close after having been stopped. Either of these occurrences cause the output at pin 9, IC304B to rapidly change in a positive direction which is inverted from IC301D. This causes a negative going signal to occur on pin 5, IC305A, NAND gate IC305A and IC305C comprise a negative set one shot multivibrator whose output appears on pin 3 and goes to a logic 0 for one-half second. This output does two things; it changes the duty cycle appearing on pin 6, IC301E by changing the transfer voltage on pin 5, IC301E from D302, and it appears as a low on pin 13, IC302D, causing pin 11, IC302D, to go high. This allows the successive stages to alternately change logic states as per the 66% duty cycle sequence, but now at a 33% duty cycle.

Troubleshooting The Valve Controller Circuit Card

Voltage Test Points For Valve Controller Circuit Card

Conditions of Test: 24V DC Input. Valve controller set at position 8 except where shown differently. Valve reset enabled. Motor not running. No tachometer input. Voltmeter at 20K ohm/V or higher. Measure regulator voltages first. All voltages ± 10% x regulator voltage error. Reference voltages to card connector pins 11 and 12 except where shown differently. REG301 - Input 22.5V, output 8.0V ± .3V.

Use Of Oscilloscope To Troubleshoot The Valve Controller Circuit Card

All waveforms taken with the flow block connected and 24V DC power.

The information that follows is for all valve controller circuit card oscillograms.

1) Signal ground is taken from card edge pins 11 and 12 except where shown differently.

2) Oscilloscope sweep at 1 millisecond/D1V. except where shown differently.

3) Oscilloscope vertical sensitivity at 2V/DIV. except where shown differently.

4) Valve reset button depressed to put the valve in its operate mode.

5) If the bottom of each waveform is not at zero Volts, an additional single straight trace represents zero, except where shown differently.

(1) TP-10.

IC305C, pin 3, 0.2 sec/DIV sweep.

Condition: Move the valve controller knob to slightly open, or close the valve. This oscillogram is of the 33% duty cycle control pulse.

(2) TP-11.

IC301E, pin 6; 66% duty cycle.

(3) TP-11.

IC301E, pin 6; 33% duty cycle.

Condition: Move the valve controller knob slightly (small amount) open, or close the valve.

(4) TP-12

IC306B, pin 1; 66% duty cycle.

Condition: Valve closing, caution lamp is on.

(5) TP-13.

Card edge pin 2 (scope common) and pin 16, motor waveform, vertical sensitivity at 5V/DIV.

The center of the scope screen is zero Volts.

Condition: Valve motor closing at 66% duty cycle.

(6) TP-13.

Card edge pin 2 (scope common) and pin 16, motor waveform, vertical sensitivity at 5V/DIV.

The center of the scope screen is zero Volts.

Condition: Valve stalled in closed position.

(7) TP-14.

IC307, pin 2; 0.2 sec sweep.

Condition: Caution lamp flashing (valve controller knob between 5.5 and 10.0).

Parts Lists And Circuit Schematics

NOTE: For parts that are not serviced by Caterpillar, write or call Flo-Tech, Inc. For repair service, return the Flow Meter, prepaid to:

Flo-Tech, Inc.
403 South Washington Blvd.
Mundelein, IL 60060, U.S.A.
Telephone: (312) 566-9120

When returning the Flow Meter to Flo-Tech, Inc. for repair, always give:

1. Description of the problem.

2. Where to send the unit after repair.

3. Name of person to whom the unit is to be returned.

4. Billing address, if it is different than the shipping address.

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