3054B Industrial Engine Caterpillar

Test Tools For The Electrical System

Most of the tests of the electrical system can be done on the engine. If the test shows a defect in a component, remove the component for more testing.

Before the electrical system is tested, the following conditions should exist:

• The wiring insulation must be in good condition.

• The wire and cable connections must be clean and tight.

• The battery must be fully charged.

4C-4911 Battery Load Tester

Illustration 1	g00283565
4C-4911 Battery Load Tester

The 4C-4911 Battery Load Tester is a portable unit. The battery load tester can be used to load test all 6 volt, 8 volt and 12 volt batteries.

The battery load tester has two heavy-duty cables. The cables can be easily fastened to the battery terminals.

A knob on the top of the battery load tester adjusts the current from the battery to a maximum of 100 amperes. The tester is cooled by an internal fan that is automatically activated when a load is applied.

The battery load tester has a LCD in order to display the voltage and the amperage.

Refer to the Tool Operating Manual, SEHS9249 for operating instructions for the 4C-4911 Battery Load Tester.

8T-0900 Ammeter

Illustration 2	g00293221
8T-0900 Ammeter

The 8T-0900 Ammeter is a portable instrument for measuring electrical current. The ammeter measures the electrical current without interrupting the circuit or damaging the insulation on the conductors.

The ammeter has a digital display of 1 to 1200 amperes for indicating the current . If a 6V-6014 Cable is connected between the ammeter and the digital multimeter, current readings of less than 1 ampere can be displayed on the multimeter.

A lever is used to open the jaws of the ammeter in order to place the jaws on an electrical conductor. The current is measured when the jaws surround the electrical conductor. The diameter of the electrical conductor cannot exceed 19 mm (0.75 inch).

A trigger switch that can be locked in the ON or OFF position is used to turn on the ammeter. When the trigger is released, the last current reading remains on the display for five seconds. Retaining the reading allows accurate measurements to be taken in areas with limited access when the digital display is not visible to the operator.

Power for the ammeter is produced by batteries which are located inside the handle.

Refer to Special Instruction, SEHS8420 for operating instructions for the 8T-0900 Ammeter.

6V-7070 Digital Multimeter

Illustration 3	g00283566
6V-7070 Digital Multimeter

The 6V-7070 Digital Multimeter is a portable instrument.

The digital multimeter has seven functions and 29 ranges. A digital display indicates the measurement. The digital multimeter measures resistance in ohms. This capability permits continuity checks for fast circuit inspection. The digital multimeter can also be used for troubleshooting small capacitors.

Battery

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Personal injury can result from battery fumes or explosion. Batteries give off flammable fumes that can explode. Electrolyte is an acid and can cause personal injury if it contacts the skin or eyes. Prevent sparks near the batteries. Sparks could cause vapors to explode. Do not allow jumper cable ends to contact each other or the engine. Improper jumper cable connections can cause an explosion. Always wear protective glasses when working with batteries.

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. The alternator may be damaged if both of the following conditions occur:

• The alternator is in operation.

• The circuit between the battery and the alternator is broken.

The damage can occur when the load on the battery is lost. The lost load on the battery causes a sudden increase in the voltage. This high voltage can damage the charging unit, the regulator, and other electrical components.

The 4C-4911 Battery Load Tester is used to load test a battery that does not hold a charge.

Refer to the Tool Operating Manual, SEHS9249 for instructions on the use of the 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS7633 for the correct procedures and specifications for testing batteries.

Starting Motor

Illustration 4	g00318603
Starting circuit for 12 volt system (typical example) (1) Test point (2) Test point (3) Test point (4) Test point (5) Test point (X) Hold-in coil (W) Pull-in coil

Procedures For Diagnosis Of The Starting Motor

The procedures for diagnosing the starting motor are intended to help the serviceman determine if a starting motor needs to be replaced or repaired. The procedures are not intended to cover all possible problems and conditions. The procedures serve only as a guide. The most common 12 volt circuit is shown in Illustration 4.

General Information

All electrical starting systems have four elements:

• Ignition switch

• Start relay

• Starting motor solenoid

• Starting motor

Start switches have a capacity of 5 to 20 amperes. The coil of a start relay draws about 1 ampere between test points (1) and (2). The switch contacts of the start relay for the starting motor are rated between 100 and 300 amperes. The start relay can easily switch the load of 5 to 50 amperes for the starting motor solenoid.

The starting motor solenoid is a switch with a capacity of about 1000 amperes. The starting motor solenoid has two functions:

• The pinion gear is engaged with the ring gear of the flywheel.

• The starting motor is rotated.

The starting motor solenoid has two coils. Pull-in coil (W) draws about 40 amperes. Hold-in coil (X) requires about 5 amperes.

When the start relay closes, coils (W) and (X) receive power. Battery voltage is applied to test point (3), which is the start terminal (S). Terminal "G"of the coil (X) is permanently grounded to the ground post or the housing of the starting motor. Grounding for the test point (4) of the pull-in coil (W) is momentary. This ground takes place through the DC resistance of the starting motor.

When the magnetic force increases in both coils, the pinion gear moves toward the ring gear of the flywheel. Then, the solenoid contacts close in order to provide power to the starting motor. When the solenoid contacts close, the ground is temporarily removed from the pull-in coil (W). Battery voltage is supplied on both ends of the pull-in coil while the starting motor cranks. During this period, the pull-in coil is out of the circuit.

Cranking of the engine continues until current to the solenoid is stopped by releasing the ignition switch.

Power which is available during cranking varies according to the temperature and condition of the batteries. The following chart shows the voltages which are expected from a battery at the various temperature ranges.

The following table shows the maximum acceptable loss of voltage in the battery circuit. The battery circuit supplies high current to the starting motor. The values in the table are for engines which have service of 2000 hours or more.

Voltage drops that are greater than the amounts in Table 3 are caused most often by the following conditions:

• Loose connections

• Corroded connections

• Faulty switch contacts

Diagnosis Procedure

If the starting motor does not crank or cranks slow, perform the following procedure:

1. Measure the voltage of the battery at the battery posts with the multimeter when you are cranking the engine or attempting to crank the engine. Measure the voltage across the battery posts. Do not measure the voltage across the cable post clamps.

2. Battery voltage

   1. If the voltage is equal or greater than the voltage in Table 2, then go to Step 3.

   2. The battery voltage is less than the voltage in Table 2.

      Refer to Special Instruction, SEHS7633 in order to test the battery.

      A low charge in a battery can be caused by several conditions.

      • Deterioration of the battery

      • A shorted starting motor

      • A faulty alternator

      • Loose drive belts

      • Current leakage in another part of the electrical system

3. Measure the current that is between the positive battery post and the starting motor solenoid. Use the 8T-0900 Ammeter. Refer to the Specifications, "Starting Motor" for the maximum current that is allowed for no load conditions.

   Note: If the following conditions exist, do not perform the test in Step 3 because the starting motor has a problem.

   • The voltage at the battery post is within 2 volts of the lowest value in the applicable temperature range of Table 2.

   • The large starting motor cables get hot.

   The current and the voltages that are specified in the Specifications module are measured at a temperature of 27 °C (80 °F). When the temperature is below 27 °C (80 °F), the voltage will be lower through the starting motor. When the temperature is below 27 °C (80 °F), the current through the starting motor will be higher. If the current is too great, a problem exists in the starting motor. Repair the problem or replace the starting motor.

4. Use the multimeter in order to measure the voltage of the starting motor. Measure the voltage from test point (4) to test point (5) when you are cranking or attempting to crank the engine.

5. Voltage across test points (4) and (5)

   1. If the voltage is equal to the voltage that is listed in Table 2, then the battery and the starting motor cable that goes to the starting motor are within specifications. Go to Step 8. If the voltage is greater than the voltage that is listed in Table 2, then the battery and the starting motor cable that goes to the starting motor are within specifications. Go to Step 8.

   2. The starting motor voltage is less than the voltage specified in Table 2.

      The voltage drop between the battery and the starting motor is too great. Go to Step 6.

6. Measure the voltage drops in the cranking circuits with the multimeter. Compare the results with the voltage drops which are allowed in Table 3.

7. Voltage drops in the cranking circuits

   1. Voltage drops are equal to the voltage drops that are listed in Table 3 or the voltage drops are less than the voltage drops that are listed in Table 3. Go to Step 8 in order to check the engine.

   2. The voltage drops are greater than the voltage drops that are listed in Table 3. The faulty component should be repaired or replaced.

8. Rotate the crankshaft by hand in order to ensure that the crankshaft rotates freely. Check the oil viscosity and any external loads that could affect the engine rotation.

   1. If the crankshaft is stuck or difficult to turn, repair the engine.

   2. If the engine is not difficult to turn, go to Step 10.

9. Attempt to crank the starting motor.

   1. The starting motor cranks slowly.

      Remove the starting motor for repair or replacement.

   2. The starting motor does not crank.

      Check for the blocked engagement of the pinion gear and flywheel ring gear.

      Note: Blocked engagement and open solenoid contacts will give the same electrical symptoms.

Start Relay Tests

If the engine does not start, perform these tests in order to find any fault of the start relay.

9G-4368 Relay

Illustration 5	g00295931
9G-4368 Relay

The following test is with battery current.

1. Put the multimeter on the 200 ohm scale. Turn the ignition switch to the ON position.

2. Put the multimeter leads on the "C1" and "C2" terminals. The resistance across the leads (1) should be zero ohms.

   If the resistance is not zero, the start relay must be replaced.

The following test is with no battery current.

1. Disconnect the wires from the "W1" and "W2" terminals of the start relay.

2. Put the multimeter leads on each "W1" and "W2" terminal. The resistance across the leads (2) should measure 15 ± 1 ohms.

   If the resistance is not correct, replace the start relay.

3. If the resistance is correct, disconnect the "C1" and "C2" terminals. Use the 8T-0500 Continuity Test Light between the "C1" and "C2" terminal. The test light should not turn on. Then, move the probe of the test light from the "C2" terminal to the "C4" terminal. The test light should not turn on.

   If the test light turns on for either test, the start relay must be replaced.

4. If the start relay is not faulty, refer to Troubleshooting for other tests of the starting system.

069-5466 Relay

Illustration 6	g00295932
069-5466 Relay

The following test is performed with battery current.

1. Put the multimeter on the 200 ohm scale. Turn the ignition switch for the engine to the ON position.

2. Put the multimeter leads on the terminals "4" and "7". Put the multimeter leads on the terminals "6" and "9".

   The resistance must be zero ohms across both sets of terminals.

   If the resistance is not zero, the start relay must be replaced.

The following test is with no battery current.

1. Disconnect the wires from the "A" and"B" terminals of the start relay.

2. Put the multimeter leads on the terminals "A" and "B" terminal.

   The resistance should be between 30 and 34 ohms.

   If the resistance is not correct, replace the start relay.

3. If the resistance is correct, disconnect the terminals "4", "7", "6" and "9".

4. Put the leads of the 8T-0500 Continuity Test Light between the terminals "4" and "7". The test light should not turn on. Put the leads of the test light on the terminals "6"and "9". The test light should not turn on.

   If the test light turns on, the start relay must be replaced.

5. If the start relay is not faulty, refer to the Troubleshooting for other tests of the starting system.

Charging System

The condition of the charge in the battery at each regular inspection will indicate if the charging system operates correctly. A problem exists when the battery is constantly in a condition of low charge. A problem also exists if more than one ounce of water must be added to a cell in the battery during the following periods:

• One week

• Each 100 hours of operation

Testing the charging system is preferable when the following conditions exist:

• The alternator is mounted on the engine.

• The voltage regulator is mounted on the engine.

• The wiring and electrical components which are used in the test are a permanent part of the electrical system.

Bench testing can be done on the alternator and the voltage regulator. This testing will determine if the individual component is faulty.

When a component is replaced or repaired, the charging system should be tested. This test will verify that the charging system is operating correctly.

Refer to Specifications, "Alternator and Regulator" for additional information.

Before the charging system is tested on the engine, the charging system and the battery must be inspected. Use the following inspection procedures:

1. The battery must be charged to at least 75% of rated power output. The specific gravity of the solution in the battery should be 1.225. The battery should be held firmly in place. The battery holder must not put too much stress on the battery.

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

3. The leads, the junctions, the switches, and the panel instruments which relate to the charging system must operate correctly.

4. The alternator and the drive components for the alternator must operate correctly.

Alternators

1. Put the positive lead "+" of the multimeter on the "Bat" terminal of the alternator. Put the negative "-" lead on the ground terminal or on the frame of the alternator. Put the ammeter around the positive output wire of the alternator.

2. Turn off all electrical accessories. Turn off the fuel to the engine. Crank the engine for 30 seconds. Wait for two minutes in order to cool the starting motor. If the electrical system appears to operate correctly, crank the engine again for 30 seconds.

   Note: Cranking the engine for 30 seconds partially discharges the batteries in order to do a charging test. If the battery has a low charge, do not perform this step. Jump start the engine or charge the battery before the engine is started.

3. Start the engine and run at full throttle.

4. Check the output current of the alternator. The initial charging current should be equal to the minimum full load current or the initial charging current should be greater than the minimum full load current. Refer to Specifications, "Alternator and Regulator" for the correct minimum full load current at different rpm.
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   Table 6

   Fault Conditions And Possible Causes
   Current At Start-up	The Voltage Is Below The Specification After 10 Minutes.	The Voltage Is Within The Specification After 10 Minutes.	The Voltage Is Above The Specification After 10 Minutes.
   Less than the specifications	Replace the alternator. Check the circuit of the ignition switch.	Turn on all accessories. If the voltage decreases below the specifications, replace the alternator.	-
   Decreases after matching specifications	Replace the alternator.	The alternator and the battery match the specifications. Turn on all accessories in order to verify that the voltage stays within specifications.	Replace the alternator.
   The current consistently exceeds the specifications.	In order to test the battery, follow the procedures that are in the Tool Operation Manual, SEHS7633. Test the alternator again.	The alternator operates within the specifications. In order to test the battery, follow the procedures that are in the Tool Operation Manual, SEHS7633.	Replace the alternator. Inspect the battery for damage.

5. After approximately ten minutes of operating the engine at full throttle, the output voltage of the alternator should be 14.0 ± 0.5 volts for a 12 volt system. After approximately ten minutes of operating the engine at full throttle, the output voltage of the alternator should be 28.0 ± 1 volts for a 24 volt system. Refer to the Fault Conditions And Possible Causes in Table 6.

6. After ten minutes of engine operation, the charging current should decrease to approximately 10 amperes. The actual length of time for the charging current to decrease to 10 amperes depends on the following conditions:

   • The battery charge

   • The ambient temperature

   • The rpm of the engine

   Refer to the Fault Conditions And Possible Causes in Table 6.