Refrigerant Compressor Functional Test for All Caterpillar Machines{1802} Caterpillar

Agricultural Tractor: All

Articulated Truck: All

Asphalt Paver: All

Backhoe Loader: All

Challenger: All

Cold Planer: All

Combine: All

Compact Wheel Loader: ALL

Earthmoving Compactor: All

Excavator: All

Forest Products: All

Integrated Toolcarrier: All

Landfill Compactor: All

Load Haul Dump: All

Mini Hydraulic Excavator: All

Motor Grader: All

Multi Terrain Loader: All

Paving Compactor: All

Off-Highway Truck/Tractor: All

Road Reclaimer/Soil Stabilizer: All

Skid Steer Loader: All

Soil Compactor: All

Telehandler: All

Track-Type Loader: All

Track-Type Skidder: All

Track-Type Tractor: All

Underground Articulated Truck: All

Wheel Dozer: All

Wheel Feller Buncher: All

Wheel Loader: All

Wheel Skidder: All

Wheel Tractor-Scraper: All

Introduction

Reference: Specifications, SENR5664, "Air Conditioning and Heating R-134a for All Caterpillar Machines"

The purpose of this instruction is to identify functioning compressors before they are removed from a machine. Functioning compressors should produce both high and low pressure. If the compressor fails any one of Steps 3, 5, 7, or 8 listed below, then it is considered a failed compressor. Please list in the Warranty Claim Story the step(s) the compressor failed during functional testing.

Note: In the event the compressor is considered "failed", the air conditioning system should be further diagnosed to find and repair the root cause of the failure, for example a fitting leak. In the event the compressor is considered "good", additional assistance with A/C system diagnosis can be found in Service Manual, SENR5664, "Air Conditioning and Heating R134a for all Caterpillar Machines" or by contacting your Caterpillar dealer.

Procedures

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Personal injury can result from contact with refrigerant. This system is under pressure at all times, even if the engine is not running. Heat should never be applied to a charged system. Contact with refrigerant can cause frost bite. Keep face and hands away to help prevent injury. Protective goggles must always be worn when refrigerant lines are opened, even if the gauges indicate the system is empty of refrigerant. Always use caution when a fitting is removed. Slowly loosen the fitting. If the system is still under pressure, evacuate the system recovering the refrigerant before removing the fitting. Personal injury or death can result from inhaling refrigerant through a lit cigarette. Inhaling air conditioner refrigerant gas through a lit cigarette or other smoking method or inhaling fumes released from a flame contacting air conditioner refrigerant gas, can cause bodily harm or death. Do not smoke when servicing air conditioners or wherever refrigerant gas may be present. Before any checks of the air conditioning and heating system are made, move the machine to a smooth horizontal surface. Lower all implements to the ground. Make sure the transmission is in neutral or park and that the parking brake is engaged. Keep all other personnel away from the machine or where they can be seen.

1. Check the air filters. If the customer complaint is poor cab cooling, past experience has shown that plugged air filters can often be the cause. Most A/C systems have return air filters and fresh air filters. Be sure to check both the return air filters and fresh air filters.

   Air Filters Checked? Yes/No

2. Test the voltage. With the engine running and the air conditioning switched ON, check if the voltage at the compressor is a minimum of 11.5VDC for a 12VDC system or 23 volts for a 24VDC system. Be sure to switch ON all electrical loads that the customer may be using on his machine on a routine basis. A customer added lighting systems, for example, could load the electrical supply system to the point that available voltage is decreased below specification.

   Voltage Checked? Yes/No

   Measured Voltage Level: ____ (volts)

   Note: For A/C systems with a Compressor Protection System (CPS), there will be approximately a 30 seconds delay before a voltage signal will be detected at the compressor after the A/C is switched ON. A/C systems with CPS can be identified by the use of either the 169-7443 On Delay Timer As or the 212-2204 Air Conditioner Control Gp . In most applications the electronic control group is located near the compressor.

3. Test the resistance. Measure resistance of the clutch coil at the compressor connector. For 12VDC models, measured resistance should be within -0.3 to +1.1 ohms of the amount listed in the Specifications section of Service Manual, SENR5664, "Air Conditioning and Heating R134a for all Caterpillar Machines", "Refrigerant Compressor". For 24VDC models, measured resistance should be within -1.3 to +5.5 ohms of the amount listed in the SENR5664 Specifications Section. The resistance range listed above compensates for the effect of temperature on the coil. The values listed in SENR5664 are nominal for 20 °C (68 °F).

   Resistance Checked? Yes/No

   Measured Resistance Level: ____ (ohms)

4. Check the belt tension. For new and old belts, use the 144-0235 Belt Tension Gauge . For a new belt installation, the initial belt tension for a compressor drives system without an auto tensioning device should be 534 N (120 lb). For used belts, the belt tension should be 400 N (90 lb).

   Belt Tension Checked? Yes/No

   Measured Belt Tension: ____ (N) or (lbs) - before adjust

   Measured Belt Tension: ____ (N) or (lbs) - after adjust

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Accidental machine starting can cause injury or death to personnel working on the machine. To avoid accidental machine starting, turn the battery disconnect switch to the OFF position and remove the key. If the machine is not equipped with a battery disconnect switch, disconnect the battery cables from the battery and tape the battery clamps. Place a do not operate tag at the battery disconnect switch location to inform personnel that the machine is being worked on.

Note: The electrical power supply to the compressor should be switched OFF to perform this test.

5. Test the rotation. Rotate the compressor in the direction of belt travel by turning the nut on the end of the compressor main shaft. Rotation should be smooth with no binding.

   Rotation Checked? Yes/No

   Rotation Smooth? ____ (Yes) or (No)

6. Check the charge level confirmation. The air conditioning system must be correctly charged per Caterpillar specification or an incorrect diagnosis will occur. The best method to achieve the correct system refrigerant charge is by recovering, evacuating, and recharging with clean refrigerant to the correct level. Charging the A/C system must be conducted by weighing refrigerant with a calibrated scale to insure accuracy. Also, be sure to replace oil removed during refrigerant recovery with new oil. Reference SENR5664 for refrigerant charging procedures and capacity of CAT A/C systems.

   Charge Level Checked? Yes/No

   Oil Removed During Recovery: ____ (ml) or (oz)

   Refrigerant Charge Amount: ____ (Kg) or (lbs)

7. Test for low pressure. This test is best performed with the machine parked in the shade and with ambient temperatures less than 30 °C (86 °F). Close all cab doors and windows, block fresh airflow into the cab, and bypass the low-pressure switch (if the air conditioning system is so equipped). Start the machine and operate at high idle with the air conditioning switched ON and the cab blower set on low. Measure the low-side pressure at the refrigerant compressor after 10-15 minutes of operation. If the pressure reading is less than 69 kPa (10 psi) then the compressor suction valves are operating correctly.

   Low Pressure Checked? Yes/No

   Record Low Pressure Reading: ____ (kPa) or (Psig)

   Note: If cab temperature is above 25 °C (77 °F) when starting the test, the cab blower may require high-speed setting to reduce the temperature before starting the procedure.

8. Test for high pressure. Start the engine and set the speed at approximately 1200 rpm. Turn the air conditioner ON. Place a sheet of cardboard over the condenser to block airflow. Limiting the airflow over the condenser will cause compressor discharge pressure to increase. Check if the compressor discharge is able to increase up to 2414 kPa (350 psi). Once the specified pressure is reached, immediately remove the cardboard. If the compressor passes the test, the discharge valves are operating correctly.

   High Pressure Checked? Yes/No

   Record High Pressure Reading: ____ (kPa) or (Psig)

The functional test is now complete. If this test procedure results in inconclusive results, your dealership's Technical Communicator can report the problem using the on-line Dealer Solution Network. The Dealer Solution Network will provide your Technical Communicator with additional troubleshooting support.

Illustrations 1 through 4 are provided as Good Air Conditioning System Practices and Troubleshooting Tips.

Illustration 1	g01127048
Typical Refrigerant Compressor ( 3E-1906 Refrigerant Compressor Gp shown)

Illustration 2	g01123619
Wire lead and pin location for field coil

Illustration 3	g01126988
Permissible mounting orientation and location of Suction Port "S" and Discharge Port "D". (1) Suction Port "S" (2) Discharge Port "D"

Illustration 4	g01127111
On-Delay Timer Assembly (Compression Protection System)

Procedure to Test the On-Delay Timer Assembly

In order to diagnose a faulty on-delay timer assembly for the refrigerant compressor, the engine start switch must be in the ON position and the air conditioning switch must be activated.

Note: The on-delay timer assembly will delay the power supply to the compressor clutch coil for 30 seconds after the air conditioning switch is activated.

1. Separate the four-pin connector from the wiring harness.

2. In order to check that power is getting from the on-delay timer to the compressor, perform the following steps:

   1. Set the 146-4080 Digital Multimeter Gp to DC voltage.

   2. Connect the multimeter's positive probe to pin 4 on the wiring harness.

   3. Connect the multimeter's negative probe to a suitable ground. The multimeter should read 24VDC for 24 volt machines. The multimeter should read 12VDC for 12 volt machines.

      Note: On a 24-volt system, if the voltage is below 18VDC or if the voltage is above 32VDC, the on-delay timer will not supply power to the compressor. On 12-volt systems, the range is 9VDC to 24VDC.

3. Set the 146-4080 Digital Multimeter Gp to OHMS. Connect the multimeter's positive probe to pin location 2 on the wiring harness. Connect the multimeter's negative probe to a suitable chassis ground. The multimeter will display OL if the ground is not present.

4. Set the 146-4080 Digital Multimeter Gp to OHMS. Connect the multimeter's positive probe to pin location 1 on the wiring harness. Connect the multimeter's negative probe to a suitable chassis ground. If the multimeter displays "OL", one of the three switches is open. If an open condition occurs, check each of the switches.

   Note: There must be refrigerant in the air conditioning system in order to close both of the pressure switches.

5. In order to check that power is getting from the on-delay timer assembly to the compressor clutch coil, reconnect the on-delay timer assembly to the wiring harness.

   1. Set the 146-4080 Digital Multimeter Gp to DC voltage.

   2. Remove the 2-pin connector from the compressor clutch coil.

   3. Connect the negative probe to a suitable chassis ground.

   4. Check each of the two pins on the wiring harness for voltage. On a 24-volt system, one of the pins should supply 24 VDC. On a 12-volt system, one of the pins should supply 12 VDC.

6. In order to check the ground path from the compressor clutch coil to the chassis:

   1. Turn Off the air conditioning switch in the cab.

   2. Set the 146-4080 Digital Multimeter Gp to Ohms.

   3. Remove the two-pin connector from the compressor clutch coil.

   4. Connect the negative lead to a suitable ground.

   5. Check each of the two pins on the two-pin connectors for continuity. One of the two pins should display "OL".

7. If both the correct ground and voltage are present, check the resistance of the compressor clutch coil. Refer to the Specifications section in Service Manual, SENR5664, "Air Conditioning and Heating R134a for all Caterpillar Machines", "Refrigerant Compressor".