G3408 and G3412 Engines Caterpillar

Test Tools For The Electrical System

Most of the tests of the electrical system can be done on the engine. The wiring insulation must be in good condition. The wire and cable connections must be clean and tight. The battery must be fully charged. If the on-engine test shows a defect in a component, remove the component for more testing.

The service manual Testing And Adjusting Electrical Components, REG00636 has complete specifications and procedures for the components of the starting circuit and the charging circuit.

The 8T-0900 Ammeter is completely portable. This ammeter is a self-contained instrument that measures electrical currents without breaking the circuit and without disturbing the conductor's insulation.

Illustration 1	g00296441
8T-0900 Ammeter

The ammeter contains a digital display that is used to monitor current directly within a range between 1 ampere and 1200 amperes. If an optional 6V-6014 Cable is connected between this ammeter and a digital multimeter, current readings can be viewed directly from the display of the multimeter. This can be accomplished under only one condition:

• The readings are less than 1 ammeter.

A lever opens the ammeter's jaws over a conductor. The conductor's diameter can not be larger than 19 mm (0.75 inch).

The spring loaded jaws close around the conductor. A trigger switch controls the ammeter. The trigger switch can be locked into the ON position or into the OFF position.

After the trigger has been turned to the OFF position, the reading will remain on the digital display for five seconds. This accurately measures currents in areas with limited access. For example, these areas include areas that are beyond the operator's sight. An ammeter for DC operation contains a zero control. This ammeter has batteries that supply the power for operation. The batteries are located in the handle of the ammeter.

Note: Refer to Special Instruction, SEHS8420 for more information about using the 8T-0900 Ammeter.

Illustration 2	g00283566
6V-7070 Digital Multimeter

The 6V-7070 Digital Multimeter is a portable, hand-held service tool with a digital display. This multimeter is built with extra protection against damage that may occur in field applications. The multimeter is equipped with 7 functions and 29 ranges. The 6V-7070 Digital Multimeter has an instant ohms indicator. This indicator permits checking continuity for a fast inspection of the circuits. The multimeter can also be used for troubleshooting capacitors with small values.

Note: Refer to Special Instruction, SEHS7734.

Battery

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Never disconnect any charging unit circuit or battery circuit cable from the battery when the charging unit is operated. A spark can cause an explosion from the flammable vapor mixture of hydrogen and oxygen that is released from the electrolyte through the battery outlets. Injury to personnel can be the result.

The battery circuit is an electrical load on the charging unit. The load is variable because of the condition of the charge in the battery.

Use the 4C-4911 Battery Load Tester in order to test a battery that does not maintain a charge when the battery is active. Refer to Operating Manual, SEHS9249 for detailed instruction on the use of the 4C-4911 Battery Load Tester. See Special Instruction, SEHS7633 for the correct procedure and for the specifications to use when you test the batteries.

Charging System

The condition of charge in the battery at each regular inspection will show if the charging system operates correctly. An adjustment is necessary when the battery is constantly in a low condition of charge or when a large amount of water is needed. A large amount of water would be more than one ounce of water per cell per week or per every 50 service hours.

When it is possible, make a test of the charging unit and voltage regulator. Use wiring and components that are a permanent part of the system. Off-engine testing or bench testing will give a test of the charging unit and voltage regulator operation. This testing will give an indication of needed repair. After repairs are made, perform a test in order to prove that the units have been repaired to the original condition of operation.

Before the start of on-engine testing, the charging system and the battery must be checked according to the following steps.

1. The battery must be at least 75 percent (1.225 Sp Gr) of the full charge. The battery must be held tightly in place. The battery holder must not put too much stress on the battery.

2. Cables between the battery, the starter, and the engine ground must be the correct size. Wires and cables must be free of corrosion. Wires and cables must have cable support clamps in order to prevent stress on battery connections (terminals).

3. Leads, junctions, switches, and panel instruments that have direct relation to the charging circuit must give correct circuit control.

4. Inspect the drive components for the charging unit in order to be sure that the components are free of grease and oil. Be sure that the drive components have the ability to operate the charging unit.

Alternator Regulator Adjustment

(Delco-Remy)

The charging rate of the alternator should be checked when an alternator is charging the battery too much. The charging rate of the alternator should be checked when an alternator is not charging the battery enough. Make reference to the Specifications module in order to find all testing specifications for the alternators and regulators.

To adjust the voltage setting, use the following procedure:

3T-6352 Alternator And 6N-9294 Alternator

No adjustment can be made in order to change the rate of charge on the alternator regulators. If the rate of charge is not correct, a replacement of the regulator is necessary.

Illustration 3	g00346692
6N-9294 Alternator (1) Output terminal. (2) Relay terminal. (3) Ground screw.

4N-3986 Alternator

To adjust the voltage output, use the following procedure.

1. Pull out the voltage adjustment cap (1) .

2. Turn the voltage adjustment cap (1) .

   Turn the cap. ... 90 degrees

3. Install the voltage adjustment cap into the alternator.

The voltage adjustment cap has four positions.

• HI

• LO

• The two positions between the high setting and the low setting

Illustration 4	g00346832
Cap type regulator adjustment (1) Voltage adjustment cap.

Tightening The Alternator Pulley Nut

Illustration 5	g00283568
Tools for tightening the alternator pulley nut (1) 8T-9293 Torque Wrench. (2) 8S-1588 Adapter. (3) 2P-8267 Hex Bit Socket. (4) 8H-8517 Combination Wrench. (5) 8T-5314 Adapter Socket .

Tighten the nut that holds the pulley with the tools shown.

Tighten the nut to the following torque. ... 100 ± 10 N·m (73.76 ± 7.38 lb ft)

Starting System

Note: Refer to Special Instruction, SEHS7006 for complete information for the use of the 5P-0300 Electrical Tester .

Use the multimeter in the DCV range to find starting system components which do not function.

Move the start control switch in order to activate the starting solenoids. The starting solenoid's operation can be heard as the pinions of the starting motor are engaged with the ring gear on the engine flywheel.

If a solenoid for a starting motor will not operate, it is possible that the current from the battery did not reach the solenoid. Fasten one lead of the multimeter to the connection (terminal) for the battery cable on the solenoid. Put the other lead to a good ground. A zero reading indicates that there is a broken circuit from the battery. More testing is necessary when there is a voltage reading on the multimeter.

The solenoid operation also closes the electric circuit to the motor. Connect one lead of the multimeter to the solenoid connection (terminal) that is fastened to the motor. Put the other lead to a good ground. Activate the starting solenoid and look at the multimeter. A reading of the battery voltage shows that the problem is in the motor. The motor must be removed for further testing. A zero reading on the multimeter shows that the solenoid contacts do not close. This is an indication of the need for repair to the solenoid or an adjustment to be made to the starting motor pinion clearance.

Perform a test. Fasten one multimeter lead to the connection (terminal) for the small wire at the solenoid and fasten the other lead to the ground. Look at the multimeter and activate the starting solenoid. A voltage reading shows that the problem is in the solenoid. A zero reading indicates that the problem is in the start switch or in the wires for the start switch.

Fasten one multimeter lead to the start switch at the connection (terminal) for the wire from the battery. Fasten the other lead to a good ground. A zero reading indicates a broken circuit from the battery. Make a check of the circuit breaker and wiring. If there is a voltage reading, the problem is in the start switch or in the wires for the start switch.

Starting motors that operate too slowly can have an overload because of too much friction in the engine that is being started. Slow operation of the starting motors can also be caused by a short circuit, loose connections and/or dirt in the motors.

Refer to the Specification module for the correct output of the starter motors and the starter solenoids.

Pinion Clearance Adjustment (Delco-Remy)

When the solenoid is installed, make an adjustment of the pinion clearance. The adjustment can be made with the starting motor removed.

Illustration 6	g00301360
The connection for checking pinion clearance (1) Connector from MOTOR terminal on solenoid to motor. (2) SW terminal. (3) Ground terminal.

1. Install the solenoid without connector (1) to the motor. Install this solenoid from the "MOTOR" connections (terminal) on the solenoid to the motor.

2. Connect a battery, that has the same voltage as the solenoid, to the "SW" terminal (2) .

3. Connect the other side of the battery to connector (3) .

4. For a moment, connect a wire from the solenoid connection (terminal) to the ground connection (terminal). The solenoid connection is marked "MOTOR". The pinion will shift to the crank position and the pinion will stay there until the battery is disconnected.

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Illustration 7	g00283574
Pinion clearance adjustment (4) Shaft nut. (5) Pinion. (6) Pinion Clearance.

5. Push the pinion toward the end with the commutator in order to remove free movement.

6. Pinion clearance (6) must be 9.1 mm (0.36 inch).

7. In order to adjust the pinion clearance, remove the plug and turn the shaft nut (4) .

Pinion Clearance Adjustment (Prestolite)

There are two adjustments on this type of motor. The first type of adjustment is the end play for the armature. The second type of adjustment is the pinion clearance.

End Play For The Armature

The correct end play for the armature is 0.13 to 0.76 mm (0.005 to 0.030 inch). The adjustment is made by adding or by removing thrust washers on the commutator end of the armature shaft.

Pinion Clearance Adjustment

1. To adjust the pinion distance, connect the 24 Volt solenoid to a 12 volt battery. This connection can also be made for a 12 Volt solenoid to a 6 Volt battery. For a moment, connect a wire from the solenoid connection (terminal) to the stud (1) in the commutator end. The solenoid connection is marked "MOTOR". The solenoid and the drive will shift to the crank position.

   Disconnect the wire.

   Note: The drive will remain in the cranking position until the battery is disconnected.

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Illustration 8	g00346919
Connections for adjustment of the pinion clearance (1) Stud.

2. Push the drive toward the commutator end of the motor in order to remove free movement in the linkage. Measure the distance between the outside edge of the drive sleeve and the thrust washer. The distance (3) must be 0.51 to 1.27 mm (0.020 to 0.050 inch).

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Illustration 9	g00346922
Pinion clearance adjustment (2) Adjusting nut. (3) Distance.

3. To adjust the distance, remove the plug and turn the nut (2) .

4. Install the plug.