I hope some folks are still active here because I’m fresh out of ideas on this thing. I have a 2006 Ram 2500 Cummins. When I bought the truck it had an issue where while the truck is running (with the lights off) the reverse lights, 3rd brake light, drivers side rear running light, and passenger side front running light would be dim lit. I did some investigating and found the main harness that runs along the frame from the front of the cab to the rear had been spliced into and some portions of it just looked cruddy. So I replaced the whole harness with a nice used one. Well this solved my light issues for about a month and now it’s back. I can fix it by disconnecting and reconnecting the plug on the passenger side tail light circuit board. After about a day the lights will mess up again. I replaced the circuit board and bulbs but it continues to do this. I rechecked the main harness and can’t find anything wrong with it. Anyone have any ideas? Thanks

 

Would sound to me like you have a ground issue

 

That’s what I thought but no grounds coming off that main harness anywhere, just a main plug in the front and all the plugs coming off of it.

 

Grounds for the tail lights are in the engine compartment..... Yeah, that makes sense...... Somewhere.... G104, left front of engine compartment, and G106, left rear of engine compartment.

 

Off course a ground issue could be anywhere in the harness between the light connector and the engine bay.

I see the connectors corroded alot