Caterpillar Monitoring System for Electronic Modular Control Panel Caterpillar

Illustration 1	g00650444
Schematic For The Left Hand/Right Hand Switch

Use this procedure when the "LH/RH" Switch will not toggle the values for the left and right exhaust temperature. Use this procedure when the "LH/RH" Switch will not toggle the values for the left and right exhaust temperature. This condition is probably caused by an undesired open circuit. An unlikely cause would be a problem with the Main Display Module.

1. Locate The Switch.

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

   2. Locate the "LH/RH" switch. If you cannot find the switch, use the Electrical System Schematic in order to assist in locating the switch.

   3. Check for loose connections and check for corroded terminal connections to the switch. Clean corroded terminals and tighten loose connections.

      Expected Result: The connections are good.

      Results:

      • OK - The connections are good. Go to 2

      • NOT OK - There is a problem with the connections. Repair the poor connections and retest the system. STOP.

2. Check The Harness.

   1. Disconnect the signal wire from the switch.

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

   3. Alternately ground the signal wire and open the signal wire.

      Expected Result: The readout alternates between the values for exhaust temperature and air inlet restriction on the left and right side of the engine.

      Results:

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

      • NOT OK - The readout does not alternate between the LH and RH values for exhaust temperature. The signal wire in the engine harness is probably shorted to ground. Go to 3.

3. Check The Harness.

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

      Note: The signal wire remains disconnected from the switch. Do not allow the contact to touch any part of the engine.

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

   3. Disconnect the engine harness from the Main Display Module. At the engine harness connector for the Main Display Module, measure the resistance between the signal contact and contact 2.

      Expected Result: The resistance is greater than 5000 ohms.

      Results:

      • YES - The resistance is greater than 5000 ohms. The harness resistance is correct. The Main Display Module has a problem. Replace the Main Display Module. See Testing And Adjusting, "Module - Replace" for more information.

      • NO - 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.