Identifying cut wires under dash - M1165A1 REV

[NDT]

I believe that none of the wires are ground, so yes you can jump the +24 to the other wires to assist with “ringing out” the circuits. Two of the wires go to and from the flasher, and two go to and from the brake light switch, so sort those out first using an ohm meter. The remaining 4 wires will supply the 4 lamp unit bulbs at the 4 corners of the truck. No flashing will occur when you jump these 4 wires.

 

[GMVguy]

I believe that none of the wires are ground, so yes you can jump the +24 to the other wires to assist with “ringing out” the circuits. Two of the wires go to and from the flasher, and two go to and from the brake light switch, so sort those out first using an ohm meter. The remaining 4 wires will supply the 4 lamp unit bulbs at the 4 corners of the truck. No flashing will occur when you jump these 4 wires.

Makes sense, thanks. Do you know where the "Two-into-one" wires go? That would narrow a couple down...

 

[GMVguy]

Well, I narrowed down the wires that go to the hazard flasher (325 A & B) and light switch (22A and 467B, both of which get 24V when Run switch on). I then connected a lead to 24v and turned the light switch on, touching the 24v lead to each of the remaining unidentified wires. No lamp unit bulb lit up or flashed... I verified headlights and running lights were on. What am I missing?

 

[NDT]

Possible burned out bulbs or bad grounds. Cut or disconnected wires elsewhere.

 

[GMVguy]

Tail lights work, as do all running lights. Don't see any cut wires. Wondering if my "ringing-out" test needs something else connected for it to work, such as one of the other wires being grounded, etc.

 

[NDT]

Tail light bulb is a different bulb from the stop/turn bulb. Suggest you check the bulbs to eliminate that possibility.