Wiring Problem?

[7DShortBed]

I`m having an issue with losing my left side brake light when lights are turned on. I have brake lights without lights on but as soon as I turn on running lights and step on brake the running light goes out and no brake light either.
Any ideas? This is a new rear light harness from Lmc truck


Bill

[VetteVet]

What does the right side do? If it works ok then I would check the grounding on the left side socket to bed mount .

[damnyankee36]

Agree. Symptoms like these are typical indicators of ground issues, usually at the tail light housings as VetteVet said.

[7DShortBed]

I think I found it. It`s in the molded plug that connects everything to the
feed from front of cab on the NEW LMC taillight harness. I pulled light socket
from left side, left it hanging, went turned on running lights and I held bulb to socket and it lit up?
Not supposed to do that! So I went and got the old junk harness, plug that in to taillamp housing laying on floor, ran a ground wire to
ground housing, turn lights on and I had brake and taillight. Started to check
new plug wires and found I had continuity between brown light wire and green
reverse wire in brown wire plug slot. Don`t have it with factory plug so
I`m going to cut off the old NOS plug and connect to my new Taiwanese
harness. I lost a lot of hair scratching my head on this one.
Another reason to use the old stuff or NOS. Aftermarket crap!



Bill