4-14. 12-VOLT ELECTRICAL SYSTEM TROUBLESHOOTING PROCEDURES (CONT).
4. TAILLIGHT(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)
12 vdc cable assembly connected to
Locknut (Item 31, Appendix I)
truck, (Para 2-9)
Packing, Preformed (Item 59, Appendix I)
Parking brake applied, (TM 9-2320-364-10)
Wheels chocked, (TM 9-2320-364-10)
The following troubleshooting procedures cover the left taillight, but they apply to both taillights.
All electrical wires and components listed in this troubleshooting procedure are illustrated and located in FO-1.
Trailer may be equipped with composite lights or LED composite lights.
Truck electrical system OK.
Does at least one taillight
operate when power is
REASON FOR QUESTION
If no taillights operate when pow-
er is applied, fault is in the 12
Light lamp faulty.
vdc cable assembly through rear
Composite light faulty.
junction box assembly. If at
Wire 1008/21-29 faulty.
least one taillight operates, fault
12 vdc cable assembly faulty.
is between wire 1008/21-29 and
Connector MC16 faulty.
Front junction box assembly
Wire 1008-20 faulty.
Rear junction box assembly
Go to Step 7 of this
LED composite light ground
wire pigtail faulty.
LED composite light faulty.
If composite lights are
installed, go to Step 2
of this Fault.
If LED composite
lights are installed, go
to Step 4.1 of this