TUBE A. 8M2779 - Caterpillar

This procedure is for an alert indicator that never FLASHES. The never FLASHING condition is most likely caused by a short to ground or a faulty EMS control (unlikely).Test Step 1. CHECK ALERT INDICATORPerform the Output Test. Observe the alert indicators for FLASHING during the Output Test. See Output Test.Expected Result:The alert indicator does NOT FLASH, but others do.Results:
OK - The EMS control is faulty.Repair: Replace the EMS control. See EMS Control Replacement.STOP
NOT OK. - Go to Test Step 2.Test Step 2. Check Alert Indicator Switch
Locate the switch which corresponds to the indicator which never FLASHES. If necessary, use the Electrical System Schematic to help in locating the switch.
Remove the signal circuit from the switch.Expected Result:The alert indicator FLASHES.Results:
OK - The circuit is operating correctly. The switch is faulty.Repair: Check or replace the switch.STOP
NOT OK - The EMS control or harness is faulty. Go to Test Step 3.Test Step 3. CHECK EMS CONTROL AND HARNESSAt the machine harness connection for the switch, measure the voltage (DCV) between the signal circuit and the ground circuit.Note: EMS controls with part numbers 3T-1321 and 3T-3136 should measure 10.0 DCV 0.5 DCV instead of 8.0 DCV 0.5 DCV.Expected Result:Voltage is 8.0 0.5 DCV.Results:
OK - EMS control is faulty.Repair: Replace the EMS control. See EMS Control Replacement.STOP
NOT OK - The EMS control or harness is faulty. Go to Test Step 4.Test Step 4. CHECK HARNESS
Turn the disconnect switch to the OFF position. The signal wire remains disconnected from the switch. Do not allow the signal wire to touch anything.
On the Electrical System Schematic, trace the signal circuit from the switch to the EMS control. Determine the signal contact (connector contact) of the machine harness at the EMS control.
Disconnect the machine harness from the EMS control.
At the machine harness connector for the EMS control, measure the resistance between the signal contact and contact 2 (ground).Expected Result:Resistance is greater than 5000 ohms.Results:
OK - The EMS control is faulty.Repair: Replace the EMS control. See EMS Control Replacement.STOP
NOT OK - The harness is faulty. The signal wire within the harness is shorted to ground.Repair: Repair or replace the harness.STOP