CONNECTOR AS 3779611 - Caterpillar

Troubleshooting the Contactor Circuits
The following troubleshooting steps will help to determine if there is a problem in the transistor circuits or a problem with the contactor.The following tips assume that neither of the contactors closed when tested. If one contactor closed and one contactor did not close, check for problems in the circuits between the pilot relay and the contactor or the contactor could be faulty.
Illustration 4 g02132985
Contactor low voltage connector (7) A1 contact (8) B1 contact
Illustration 5 g02133093
Upper photo - coil connections on the side of the contactor, lower photo - feedback circuit connections on the front side of the contactor
Refer to the connection diagram at the beginning of this procedure. Use spoon type or needle type multimeter probes to verify that 24 VDC system voltage is present at the correct contactor low voltage connector contacts. If the voltage is not present at all the expected contacts, refer to the system schematic page 8 in the back of this manual or the machine schematic to investigate the cause.
Verify that system ground is present at the correct contactor low voltage connector contacts. If the grounds are not present at all the expected contacts, refer to the system schematic page 8 in the back of this manual or the machine schematic to investigate the cause.
Turn the Battery Disconnect Switch to the OFF position. The Engine Lockout Control remains in the ON (lock out) position. With the system voltage OFF, measure for low resistance (continuity) between each of the connection points for each of the circuits that are connected between the following components:
The Motor 1 ECM and the Pilot Relay.
The assembly low voltage connector and the Pilot Relay.
The Pilot Relay and each of the positive (+) coil connections on the contactors.
The ground (-) feedback circuit connections (F) on each contactor and the mating contactor low voltage connector contact (B2, B4).
Contactor 1 feedback circuit negative contact E (wire FBBBC1) and the Motor 1 ECM connector contact J1-26 (wire FBBBC1).
Contactor 2 feedback circuit negative contact E (wire FBBBC2) and the Motor 1 ECM connector contact J1-27 (wire FBBBC2).
All of the circuits should have continuity between the listed points. If a problem has not been found in any of the circuits that have been checked, turn the Battery Disconnect Switch to the ON position in order to turn ON the 24 VDC system voltage.
In this step, the sinking driver circuit will be grounded which should cause the contactors to close. Ensure that the area in the compartment is clear before closing the contactors. 24 VDC system voltage is ON.
Using a jumper wire at the contactor low voltage connector, connect the SNK1 circuit at contact A2 to cabinet ground or to one of the ground contacts on the connector.Expected Result:Grounding the SNK1 circuit should have caused both contactors to close. Results:OK - Both of the contactors close when the SNK1 circuit is grounded. The pilot relay and the contactors are working properly.Verify again that the SNK1 circuit between the ECM and the pilot relay is not