4-13. 24 VOLT ELECTRICAL SYSTEM TROUBLESHOOTING PROCEDURES (CONT).
7. BLACKOUT STOPLIGHT(S) DO NOT OPERATE.
Tools and Special Tools
Tool Kit, General Mechanic's: Automotive
(Item 50, Appendix J)
Multimeter (Item 28, Appendix J)
Engine OFF, (TM 9-2320-364-10)
24 vdc cable assembly connected to truck,
Locknut (Item 31, Appendix I)
Packing, Preformed (Item 59, Appendix I)
Parking brake applied, (TM 9-2320-364-10)
Truck air pressure charged, (TM 9-2320-364-10)
Wheels chocked, (TM 9-2320-364-10)
The following troubleshooting procedures cover the left blackout stoplight, but they apply to both blackout stoplights.
All electrical wires and components listed in this troubleshooting procedure are illustrated and located in Figure FO-1.
Trailer may be equipped with composite lights or LED composite lights
Truck electrical system OK.
Does at least one blackout
All other trailer lights operate.
stoplight operate when
Taillights operate indicating
REASON FOR QUESTION
brakes are applied?
LED composite light ground
If no blackout stoplights operate,
fault is 24 vdc cable assembly
through wire 1678C-18. If at
least one stoplight operates,
Blackout stoplight faulty.
fault is rear junction box through
Blackout stoplight lamp faulty.
Wire 1678/23-28 faulty.
24 vdc cable faulty.
Connector MC15 faulty.
Front junction box faulty.
Wire 1678C-18 faulty.
Go to Step 6 of this
Rear junction box faulty.
If composite lights
are installed, go to
Step 2 of this Fault.
If LED composite
lights are installed, go
to Step 5 of this Fault.