All similar rocker switch LED backlight circuits are checked with this procedure. All backlight LED lamps are part of the rocker switches.
Note: These lamps are not replaceable.
The rocker switch backlight normal operation is:
Rocker switch is off - Backlight is off
Rocker switch is on - Backlight is on
If the backlight does not go off when the rocker switch is off, perform the following procedures:
Test Step 1. VERIFY THAT THE BACKLIGHT WILL NOT TURN OFF
- Turn on the keyswitch.
- Put the rocker switch in the OFF position.
- Observe the backlight.
Expected Result:
The backlight is off.
Results:
- OK - The backlight is off.
Repair: Resume normal operation.
STOP.
- Not OK - The backlight is on. Proceed to Test Step 2.
Test Step 2. CHECK THE HARNESS FOR A SHORT
- Turn off the keyswitch.
- Disconnect all related ECMs from the harness.
- Disconnect the harness from the rocker switch.
- Obtain pin and wire numbers for the backlight circuit.
Verify the pin and wire numbers with the machine Electrical Schematic.
- Measure the resistance in the harness between the contacts for the backlight and the corresponding contacts for the ECM.
Expected Result:
Each resistance is greater than 5000 ohms.
Results:
- OK - Each resistance is greater than 5000 ohms. The backlight LED lamps may have failed.
Repair: Replace the rocker switch containing the backlight LED lamps.
Proceed to Test Step 3.
- Not OK - A resistance is less than 5 ohms. The harness is shorted.
Repair: Repair or replace the harness.
Proceed to Test Step 3.
Test Step 3. PERFORM AN OPERATIONAL CHECK
- Reconnect all disconnected connectors.
- Turn on the keyswitch.
- Push the rocker switch to the ON position.
- Verify that the backlight is on.
- Push the rocker switch to the OFF position.
- Verify that the backlight is off.
Expect Result:
The backlight is on when the rocker switch is on, and the backlight is off when the rocker switch is off.
Results:
- OK - The backlight is operating properly.
Repair: Resume normal operation.
STOP.
- Not OK - The backlight is not operating properly. The ECM may have failed, however ECM failure is unlikely.
Repair: Contact your Cat® dealer. If the ECM must be replaced, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP.