FACE-EXTRUDER 1985344 - Caterpillar

Illustration 1 g02202474
Typical rocker switch with lamp circuits
(1) Typical chassis headlamp sense provides power for backlight
(2) Typical backlight circuit
(3) Typical chassis backlight intensity provides ground that is varied to control brightness for indicator lamp and backlight
(4) Typical indicator lamp circuitNote: Illustration 1 is typical. Verify pin and wire numbers with the machine Electrical Schematic before beginning these procedures.This story applies to LED backlights at rocker switches. This circuit is not monitored for diagnostics by an ECM, this fault will not generate a diagnostic code.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 offRocker switch is on - Backlight is onIf 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.Expected 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 Caterpillar dealer. If the ECM must be replaced, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".STOP