Wiring help....

[JimiGibbs]

My rear wiring harness was cut (at the plug i think) to add a trailer wiring harness. Then they used some variety color wires and spliced them in. After getting to the main wires I have connected them by wire color. Everything now works (Brakes, L&R turn & Backup) except for the running lights. I'm not getting power at the back to the blue wire..... Is there a fuse I am missing? If that one wire is bad somewhere in the wiring harness is there a way to bypass it outside the harness. Have not followed the harness up to the front. That's next.

[Ωhm]

15 hours ago, JimiGibbs said:

Is there a fuse I am missing?

 

PARK fuse (10A). PARK fuse feed 12vdc to C269_B2. When light SW is set to PARK position, C269_R (Blue wire) becomes HOT (12vdc) and feeds your running lights.

 

[JimiGibbs]

OK.... That fuse was blown. Had a 25amp in it. Put a 20 in and still no tail lights. When I turned the knob on the headlight switch I heard it blow. Bad headlight switch? I am very much a novice when it comes to auto electrical so thanks for your help.

 

[GonzoTheGreat]

It should be a 10a, using oversized fuses can be risky.

 

I had that happen to me once. All the lights worked fine until i turned the knob for gauge brightness. The switch was bad. Turns out the rheostat coil snapped and was shorting out on something behind the dash.

[Ωhm]

Disconnect C157. Using another fuse and C157 disconnected find out if the fuse stills blows when set to the PARK position. This will determine if your shorted to ground (STG) on the front half of the vehicle or the rear half of the vehicle. C157_B (Blue wire).

 

[JimiGibbs]

On 1/13/2026 at 9:06 AM, Ωhm said:

Disconnect C157. Using another fuse and C157 disconnected find out if the fuse stills blows when set to the PARK position. This will determine if your shorted to ground (STG) on the front half of the vehicle or the rear half of the vehicle. C157_B (Blue wire).

 

I disconnected and the fuse did not blow.... plugged it back in and it blew immediately. So.... what exactly does that tell me? Is there short in the blue wire in the back half? Does it rule out the switch? What would you suggest next? Try a jumper wire to the back? THANKS

[Ωhm]

1 hour ago, JimiGibbs said:

Is there short in the blue wire in the back half? Does it rule out the switch?

 

Yes and Yes

 

C158 is located under the drivers side seat. Not sure on how easy it is to get to. Instead try C159 located back by the LH taillamp. With C157 connected, disconnect C159 and try the same test using the headlamp switch with C159 disconnected.

 

[JimiGibbs]

3 hours ago, Ωhm said:

 

Yes and Yes

 

C158 is located under the drivers side seat. Not sure on how easy it is to get to. Instead try C159 located back by the LH taillamp. With C157 connected, disconnect C159 and try the same test using the headlamp switch with C159 disconnected.

 

THANKS.... Getting closer. Unplugged C159 (my whole interior is out) and it didn't blow. Plugged back in and disconnected the blue wire (previous owner cut out C159 to add a trailer harness) and the fuse did not blow. Connected blue wires and it blew. So I think that narrows it down to the tail lamp harness. The harness looks to be in pretty good shape. Only think I found was the picture below where someone spliced it back for some reason. From what I can tell it's done correctly just not sure why. What would you suggest next???

[JimiGibbs]

Just now, JimiGibbs said:

THANKS.... Getting closer. Unplugged C159 (my whole interior is out) and it didn't blow. Plugged back in and disconnected the blue wire (previous owner cut out C159 to add a trailer harness) and the fuse did not blow. Connected blue wires and it blew. So I think that narrows it down to the tail lamp harness. The harness looks to be in pretty good shape. Only think I found was the picture below where someone spliced it back for some reason. From what I can tell it's done correctly just not sure why. What would you suggest next???

Also.... the blue wire pictured above was wrapped up so it's not that shorting it out.....

[The86manche]

Isn't there supposed to be 2 blue wires for the plate lights? I feel like one could be cut and shorting somewhere in the loom there.

I would say take that harness out and pull the wires out of the loom to see what's really going on if you can

[Ωhm]

There's one blue wire that runs to all taillamp bulbs. As @The86manche mentioned follow that blue wire. Make sure that RED butt splice isn't tied to GND. Check all bulbs, make sure they're 2 filaments bulbs, except license plate bulbs. I know single filament bulbs aren't supposed to fit, but people have a way of making them fit.