3508, 3508B, 3508C, 3512, 3512B, 3512C, 3516, 3516B and 3516C Engines Caterpillar Monitoring System Caterpillar

• Left exhaust temperature value

• Right exhaust temperature value

• Left air inlet restriction value

• right air inlet restriction value

The "Doesn't Toggle" condition for the "LH/RH" switch is probably caused by an open circuit. Also, the Main Display Module has a problem (unlikely condition).

1. Locate The Switch.

   1. Turn the "ECS" switch to the OFF/RESET position.

   2. Locate the "LH/RH" switch. If necessary, use the Electrical System Schematic to assist in locating the switch.

   3. Check for loose connections or corroded terminal connections to the switch.

   4. Clean corroded terminals and tighten loose connections.

2. Check The Harness.

   1. Disconnect the signal wire from the switch.

   2. Turn the "ECS" switch to the COOLDOWN/STOP position.

   3. Ground the signal wire. Float the signal wire. Repeat Step 2.c.

      Expected Result: The Display Area should Show the "LH" value and the "RH" value for exhaust temperature and the Display Area should show the "LH" value and the "RH" value for air inlet restriction.

      Results:

      • OK - The Display Area alternates between "LH" values and "RH" values for exhaust temperature. The circuit is operating correctly. The switch has a problem. Check the switch or replace the switch.

      • Not OK - The Display Area does not alternate between "LH" values and "RH" values for exhaust temperature. The signal wire for the engine harness is probably shorted to ground. Proceed to Step 3.

3. Check The Harness.

   1. Turn the "ECS" switch to the OFF/RESET position.

      Note: The signal wire remains disconnected from the switch. Do not allow the contact to touch any other components.

   2. On the Electrical System Schematic, trace the signal wire from the switch to the Main Display Module. The contact for the signal connector is contact 19 at the Main Display Module.

   3. Disconnect the engine harness from the Main Display Module.

   4. At the engine harness connector for the Main Display Module, measure the resistance between the signal contact and contact 2 (ground).

      Expected Result: The resistance should be greater than 5000 ohms.

      Results:

      • The resistance is greater than 5000 ohms. The harness resistance is correct. The Main Display Module has a problem. Replace the Main Display Module. For more information on this subject, see Testing And Adjusting, "Module - Replace".

      • The resistance is less than 5000 ohms. The engine harness has a problem. There is a short between ground and the signal wire in the engine harness. Repair the engine harness or replace the engine harness.