Trailer Lights

[Terp84Alum]

I have a 2001 GMC with the factory 7 position trailer plug. The trailer lights have started to do some crazy things. For example, when I turn the running lights on, the left trailer light comes on bright (like brake lights) but no other lights come on. Hit the brakes and the light goes out. Is there a controller that manages the separate turn and running/brake lights that may have gone bad? Any other ideas? Thanks

[Draenor]

Sounds like there is a grounding problem.

[496 XL]

Yep, sounds like you have power to the trailer but lacking proper grounding,you need to check all trailer grounds and proper vehicle to trailer ground.Also,how does your turn signals work......missed up too?

 

rgds,

Perry

[Schlogster]

I agree with the others, it really sounds like a ground problem. I have a utility trailer that is grounded to a lug on the tongue of the trailer, but somehow loses ground to the rear. It created some really irratric stuff similar to what you are experiencing. My fix was to buy a spool of 14 guage wire and run it to several spots on the frame, insuring a good ground (exposing steel through the paint) and applying a protective coating over those connections afterward. Finally, tie that wire directly into the ground lug on your trailer plug. Also, make sure there is no oxidation of the plug contact spades... this can create a slew of other headaches

 

If none of this helps, get a volt meter and make sure your wiring meets the common trailer wiring schematics I'll supply here. Hopefully you'll solve the issue through some of these ideas.

 

One last thought, make sure that your lights don't have any corrosion between the ground lug screw on the light fixture to the metal of the trailer itself. Some trailer manufacture's are so cheap that they don't even supply a ground wire to the fixture and rely on the body to supply the circuit completion. Good Luck!