ELECTRONICS GP-MACHINE 5044980 - Caterpillar

a voltmeter between the terminal locations B (return) and C (control coil voltage) on the harness side of the connector that is for the solenoid.
As the emergency stop switch is activated, measure the voltage at the connector. Place the emergency stop switch in the RUN position.Turn the battery disconnect switch to the OFF position.Restore the wiring to the original configuration.Expected Result:The voltage is 24 3 VDC after the emergency stop switch is activated.Results:
OK - The voltage is 24 3 VDC for 2.5 seconds.Repair: The harness between the emergency stop switch and the air shutoff solenoid is OK. There may be a problem with the air shutoff solenoid. Perform the following procedure:
Disconnect the connector from the solenoid. Use a multimeter to check the resistance of the coil across terminal locations B (return) and C (control coil voltage) at the solenoid connector. The correct resistance of the coil is approximately 33 Ohms at a temperature of 25 °C (77 °F).If the condition of the solenoid is suspect, replace the solenoid.
Verify the mechanical condition of the air shutoff mechanisms. Ensure that the air shutoff mechanisms close freely without binding. Check that adequate oil pressure is reaching the valve assemblies. Perform any necessary repairs.
Check that the return circuit has continuity from terminal location B of the solenoid connector to −Battery. Perform any necessary repairs.
Verify that any repairs eliminate the original problem. Place the emergency stop switch in the RUN position.Turn the battery disconnect switch to the OFF position.Restore the wiring to the original configuration.STOP
Not OK - The voltage is not 24 3 VDC.Repair: There is a problem in the circuit from the connector for the emergency stop switch to the air shutoff solenoid. Perform the following procedure:
Check the condition of the diodes that are in the diode assembly. Ensure that the diodes are within specifications. Verify that the diodes are not short or open. Replace the diode assembly, if necessary.
If the diodes are OK, isolate each segment of the harness and check for 24 3 VDC at the following locations: Note: During the measurements, ensure that the battery disconnect switch is in the ON position. Ensure that the emergency stop switch is activated. Also, be sure to use the −Battery as a return for your measurements.
Terminal 23 at the engine interface connector
Terminal 60 at the right rail connector
Terminal 4 at the harness connector for the air shutoff (right side)
Terminal 2 at the connector for the diode assemblyPlace the emergency stop switch in the RUN position.Turn the battery disconnect switch to the OFF position.Restore the wiring to the original configuration.If voltage is 24 3 VDC at the connector for the diode assembly and the diode assembly is OK, there is a problem in the harness that is from the connector at the diode assembly and the air shutoff solenoid. Repair the harness or replace the harness. Verify that the repair resolved the original problem.If the voltage is not 24 3 VDC at one of the test locations,