HEAD 9J4991 - Caterpillar

The possible causes of this failure are listed below:
The battery is discharged or the battery is faulty.
The cables to the starter have failed.
The ignition switch has failed.
The engine is locked.
The starting motor solenoid has failed.
The starting motor has an internal problem.The following tables will be referenced in troubleshooting the starting motor.
Table 1
TYPICAL SYSTEM VOLTAGE DURING CRANKING AT VARIOUS AMBIENT TEMPERATURES
Temperature 24 Volt System 32 Volt System 64 Volt System
−23 °C (−9.4 °F) to −7 °C (19.4 °F) 12 to 16 Volts 16 to 21 Volts NA
−7 °C (19.4 °F) to 10 °C (50 °F) 14 to 18 Volts 18 to 24 Volts NA
10 °C (50 °F) to 27 °C (80 °F) 16 to 20 Volts 21 to 27 Volts NA
Table 2
MAXIMUM ACCEPTABLE VOLTAGE DROPS DURING CRANKING
Circuit 24 Volt System 32 Volt System 64 Volt System
Battery negative post to the negative terminal on the starting motor 1.4 Volts 1.9 Volts 3.8 Volts
Drop across disconnect switch 1.0 Volts 1.3 Volts 2.6 Volts
Battery positive post to the positive terminal on the solenoid 1.0 Volts 1.3 Volts 2.6 Volts
Battery terminal of the solenoid to the motor terminal of the solenoid 0.8 Volts 0.4 Volts 0.4 Volts Test Step 1. CHECK THE BATTERY VOLTAGE
Attempt to crank the engine. Measure the battery voltage with the digital multimeter. Measure the voltage at the battery posts. Do not measure the voltage at the terminal of the battery cable.
Compare the voltage to table 1. Expected Result:The battery voltage is equal to or greater than the voltage in table 1.Results:
OK - Battery voltage is correct. Go to test step 2.
NOT OK - Battery voltage is too low.Repair: Check the charging system. See Special Instruction, REHS 0354, "Charging System Troubleshooting".STOPTest Step 2. TEST THE DISCONNECT SWITCH
Ensure that the disconnect switch is in the CLOSED position.
Measure the resistance across the terminals of the disconnect switch. Expected Result:The resistance should be less than 5 ohms.Results:
OK - The resistance is less than 5 ohms. The disconnect switch is correct. Proceed to test step 3.
NOT OK - The resistance is greater than 5 ohms. The disconnect switch is not correct.Repair: Replace the battery disconnect switch.STOPTest Step 3. TEST CABLES FROM THE BATTERY TO THE STARTING MOTOR
Visually inspect the battery cable terminals for the following conditions:
Loose connections
Corroded cablesExpected Result:The cables should be clean and the cables should be tight.Results:
OK - Battery cables are in good condition. Proceed to test step 4.
NOT OK - Battery cables are incorrect.Repair: Clean the terminals or replace the terminals. Tighten the terminals.STOPTest Step 4. TEST CABLES FROM THE BATTERY TO THE STARTING MOTOR FOR VOLTAGE DROP
Attempt to crank the engine. Measure the voltage from "Mtr" terminal to ground. Expected Result:The battery voltage is less than the voltage in table 2.Results:
OK - The voltage drop is less than the specified voltage drop. Proceed to test step 5.
NOT OK - The voltage drop is greater than the specified voltage drop.Repair: Repair the cables or replace the cables. Repeat the voltage measurement. If the voltage remains low, measure the voltage drop across