C7.1 Engines for Caterpillar Built Machines Alternator

Alternator - Test

C7.1 Engines for Caterpillar Built Machines [UENR3387]

C7.1 Engines for Caterpillar Built Machines Electrical System

C7.1 Engines for Caterpillar Built Machines Electric Starting System - Test

ELECTRICAL AND STARTING SYSTEM

ALTERNATOR GP-CHARGING

C7.1 Engines for Caterpillar Built Machines Alternator - Test

Put the positive lead "+" of a suitable multimeter on the "B+" terminal of the alternator. Put the negative "-" lead on the ground terminal or on the frame of the alternator. Put a suitable ammeter around the positive output wire of the alternator.
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. For the correct procedure to jump start the engine, refer to Operation and Maintenance Manual, "Starting with Jump Start Cables".
Start the engine and run the engine at full throttle.

Check the output current of the alternator. The initial charging current should be equal to the minimum full load current or greater than the minimum full load current. The electrical load from the accessories may need to be added. Refer to Specifications, "Alternator" for the correct minimum full load current.

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Table 1
Fault Conditions And Possible Causes
Current At Start-up	The Voltage Is Below Specifications After 10 Minutes.	The Voltage Is Within Specifications After 10 Minutes.	The Voltage Is Above Specifications 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. Ensure that combined current of the accessories does not exceed the maximum output of 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. Ensure that combined current of the accessories does not exceed the maximum output of the alternator.	Replace the alternator.
The voltage consistently exceeds specifications.	-	The alternator operates within the specifications. Test the battery.	Replace the alternator. Inspect the battery for damage.

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 and 28.0 ± 1 volts for a 24 volt system. Refer to the Fault Conditions And Possible Causes in table 1. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting" for more information.
After ten minutes of engine operation, the charging current should decrease to approximately 10 amperes. The actual length of time for the decrease to 10 amperes depends on the following conditions:
- The battery charge
- The ambient temperature
- The speed of the engine
Refer to the Fault Conditions And Possible Causes in table 1. Refer to Special Instruction, REHS0354, "Charging System Troubleshooting" for more information.