3512C and 3516C Marine Auxiliary Engines Caterpillar

Switch circuits may have problems such as faulty wiring, faulty switches, or faulty connectors. Use the following diagnostic procedures in order to diagnose problems with these switch circuits and repair these switch circuits:

• Crank override switch

• Manual select switch for starter selection

• Low idle select switch

• Engine protection override switch

• Rapid start/stop switch

• Manual prelube switch

• E-stop 1

• E-stop 2

These switches are normally open or normally closed.

Illustration 1	g02982454

Illustration 2	g02600223
Schematic of the switch inputs and wiring (control assembly output connectors)

Table 1

Troubleshooting Test Steps	Values	Results
1. Check the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect the switch connectors and the engine interface connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" C. Perform a 45 N (10 lb) pull test on each of the wires in the circuit for the suspect switch. D. Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. E. Check the harness and wiring for abrasions and for pinch points from the battery to the ECM.	Connectors	Results: The wiring and connectors appear to be OK. Proceed to Test Step 2 Results: There is a problem with the wiring and/or a connector. Repair: Repair the wiring and/or the connector. Replace parts, if necessary. Ensure that all of the seals are properly connected. Verify that the repair eliminated the problem.
2. Check the Switch Circuit at the ECM for Proper Operation A. Disconnect the P1 connector. B. Refer to Illustration 1. Determine the P1 terminal locations for the suspect switch. Note: If you are troubleshooting the crank override switch, ensure that the starter motor select switch is positioned to select the left starter. Note: If there are multiple switches in a circuit, verify that all of the switches are in the same state (position). C. Connect one lead of a multimeter to the P1 terminal for the suspect switch. Connect the other lead of the multimeter to ground. If the starter motor select switch is suspect, check that there is continuity across the terminals at the switch. If necessary, replace the switch Note: Wiggle the harnesses during the following measurements in order to reveal any intermittent short condition. D. Measure the resistance between the P1 terminal for the suspect switch and ground. E. Activate the switch and measure the resistance again.	Open and short	Results: One resistance measurement indicates an open circuit. The other resistance measurement indicates a short circuit. Repair: The switch is operating correctly. Operate the engine and check the switch for proper operation. Verify that the repair eliminated the problem. If the switch does not operate correctly, there may be a short circuit between the circuit for the suspect switch and another circuit. Carefully reinspect the components. Refer to Troubleshooting, "Electrical Connectors - Inspect". Locate the short circuit and perform repairs. Verify that the repair eliminated the problem. Results: Both resistance measurements indicate an open circuit or both resistance measurements indicate a short circuit. Repair: There is a problem with the circuit for the switch. The problem could be in the switch, in the wiring, or in a connector. If the inspection does not identify the faulty component, replace the switch and test the switch again. If the problem is not resolved, repair the wiring or the connector. Replace parts, if necessary. Verify that the repair eliminated the problem.