C18 Marine Generator Set 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:

• Diagnostic reset switch

• Droop-isochronous switch

• Low idle switch

• Maintenance clear switch

• Remote engine stop switch

• Run/stop switch

The switches are normally open or normally closed.

Illustration 1	g01121934
Typical switch inputs

Test Step 1. Check the Electrical Connectors and the Wiring

1. Place the keyswitch in the OFF position.
   Show/hide table

   Illustration 2	g01146374
   Location of the Electronic Control Module (ECM) (typical example) (1) J1/P1 ECM connectors

   Show/hide table

   Illustration 3	g01146383
   Location of the customer connector (typical example) (2) P61 customer connector

2. Thoroughly inspect connectors (1) and (2). Thoroughly inspect the connections for the suspect switch. Refer to Troubleshooting, "Electrical Connectors - Inspect".
   Show/hide table

   Illustration 4	g01175187
   P1 terminals for the various switches (P1-22) Maintenance clear switch (P1-23) Remote engine stop switch (P1-40) Run/stop switch (P1-41) Diagnostic reset switch (P1-46) Droop-isochronous switch (P1-47) Low idle switch

   Show/hide table

   Illustration 5	g01175207
   P61/J61 terminals for the various switches (19) Run/stop switch (34) Droop-isochronous switch (35) Low idle switch (36) Maintenance clear switch (37) Diagnostic reset switch (39) Remote engine stop switch

3. Perform a 45 N (10 lb) pull test on each of the wires in the circuit for the suspect switch.

4. 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.

5. Check the harness and wiring for abrasions and for pinch points from the battery to the ECM.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The wiring and connectors appear to be OK. Proceed to Test Step 2.

• Not OK - 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 eliminates the problem.

  STOP

Test Step 2. Test the Switch for Proper Operation

1. Disconnect the P1 connector.

2. Refer to Table 1. Determine the P1 terminal for the suspect switch.
   Show/hide table

   Table 1

   Terminals for the Switch Inputs
   Name of the Switch	P1 Terminals	J61/P61 Terminals
   Diagnostic reset switch	41	37
   Droop-isochronous switch	46	34
   Low idle switch	47	35
   Maintenance clear switch	22	36
   Remote engine stop switch	23	39
   Run/stop switch	40	19

3. Connect one lead of a multimeter to the P1 terminal for the suspect switch. Connect the other meter lead to engine ground.

   Note: Wiggle the harnesses during the following measurements in order to reveal any intermittent short condition.

4. Measure the resistance between the P1 terminal for the suspect switch and engine ground.

5. Activate the switch and measure the resistance again.

Expected Result:

One resistance measurement indicates an open circuit. The other resistance measurement is less than ten Ohms.

Results:

• OK - One resistance measurement indicates an open circuit. The other resistance measurement is less than ten Ohms.

  Repair: The switch is operating correctly. The wiring does not have a short circuit or an open circuit. Operate the engine and check the switch for proper operation.

  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 Inspectors - Inspect". Locate the short circuit and make repairs.

  STOP

• Not OK - Both resistance measurements indicate an open circuit or both resistance measurements are less than ten Ohms.

  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.

  Carefully reinspect the components. Refer to Troubleshooting, "Electrical Inspectors - Inspect".

  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 problem is resolved.

  STOP