4-13. 24 VOLT ELECTRICAL SYSTEM TROUBLESHOOTING PROCEDURES (CONT).
12. FRONT MARKER LIGHT(S) DO NOT OPERATE (S/N YB6122 075 AND UP).
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,
Parking brake applied, (TM 9-2320-364-10)
Wheels chocked, (TM 9-2320-364-10)
The following troubleshooting procedures cover the left front side marker light, but they apply to all front
All electrical wires and components listed in this troubleshooting procedure are illustrated and located in FO-1.1.
Truck electrical system OK.
on Page 118.3
All other trailer lights operate.
REASON FOR QUESTION
If voltage is not supplied to
Are 22 to 28 vdc measured on
front marker light, marker light
Wire 1012B faulty.
wire 1012B at front marker
will not operate.
Wire 1435 faulty.
Front marker light faulty.
Repair wire 1012B (see
schematic Fig FO-1.1) or
replace trailer main wire
harness (Para 4-30.1).
Verify repair, go to Step 3
of this Fault.