Black out light problem

[cfish]

Ok, so I had two of my BOLs not working. I bought a set of new lights that weren't exact for my M1009. I spliced in the new lights and mounted them cleaned all the grounds and grounding areas on the mounts. So I turn them on one at a time as I mounted each new light. All work fine until I get to the last light. My left rear light, the center yello portion is barely visible at night. When I push the brake peddle the right rear gets bright and all red lights illuminate. The left light goes completely black. Any thoughts or suggestions?
Thanks

 

[cfish]

Nobody has any thoughts as to what may be causing this?????

 

[ThunderCracker]

So when the brake is not applied both lights work?

 

[cfish]

Yes,but,

The left rear light is very dim in the center yellow portion of the light. As if it is only getting half the current required. I need to put a volt meter on it and check for out put. And when you apply the brakes the right rear light lights up properly but the left one goes dark. Power is being robbed from it or what little current it is getting is being redistributed to the other lights and dimming it to where you can't see any light at all.

 

[AceHigh]

Sure sounds like a grounding issue.

 

[Dr.Jay]

I agree. It sounds as if you have a ground problem in the rear wire harness. If memory serves me correctly, there is a black/w white trace wire with a ring terminal bolted on the top of the LH side rear frame rail just ahead of the bumper. (it is not always in this location) check it for damage, and corrosion. This wire is the ground for the rear light harness on majority of mid 80's GM trucks (also the in tank fuel pump & sending unit ground on gasoline fuel injected trucks)

 

[cfish]

My thoughts as well. I may have to follow the grounding wire through the system and replace it all together and see what that gets me. What a royal pain this is going to be.

 

[cfish]

I found that ground point you described. Looks ok but as we all know doesn't mean a thing. I will try to replace the ring connector first and clean it up and see what that gets me.

 

[SRB1976]

I had the same problem. Turned out to be a problem with one of the lights, so I replaced with another one and it works fine

 

[cfish]

I thought might have been it as well. I was given another rear light and tried it. Same results.

 

[CUCVSRK]

I don't think it is the ground because its either its grounded and they work or its not and they don't there may be something wrong with the light itself