Wiring issue with running lights on?

[DougH]

OK I've still got some sort of strange wiring issue on my trailer.

With the ignition on my trailer lights work OK., brake lights and turn signals work. When I turn on the car headlights the running lights and brake lights on the trailer light up but now the brake and turn signals don't work. Turn off the headlights and brake/turn again work OK. I've checked all of my lights and they are all grounded directly to the trailer frame

Any idea what my problem is?

[Larwyn]

Sounds like your brake lights/turn signals are seeking ground through the running lights/tail lights. When you turn on the headlights that path goes to +12 VDC eliminating and difference in potential for the brake lights and turn signals.

Check that the white wire is grounded on both the tow vehicle and the trailer. Most likely one end or the other of that wire is not grounded.

This is my guess, because it has happened to me. Hope it helps.

[Dale M.]

Kind of agree with Larwyn.... Sounds like poor ground between trailer and TV.... Might try grabbing a set of jumper cables and clamp one end on trailer frame and other end on TV chassis . Make sure you have "clean" connection (bare metal) .. IF problem goes away, you have ground issues between TV and trailer....

Dale

[alffink]

Doug

I had a very similar problem, I chased for nearly a year, it has got to be the ground (if you have problems with your trailer lights Check the ground) so if the trailers not the problem it's got to be the TV, long story short....I ran a direct ground from the TV's battery ground to the light harness, and my lights worked fine.

[BrwBier]

Are the trailer lights LED's and are the car lights seperate turn and stop lights? If so your problem sounds a lot like the problem I had. After 25 years as a mechanic I could not explain why my lights worked the way they did. In the end I needed a powered converter box for the lights. It seems that LED's don't provided enough feedback to a non-powered converter to make the brake and turn work when the tail lights are on. Any way thats what fixed mine.
Brwbier

[Gerdo]

I would agree with the lack of a good ground.

[DougH]

BrwBier you win the prize!

Finally had a chance to look at my light issue, my tailights were 4" round LED units. Replaced them with standard lights and everything now works OK
Sure had me stumped and wouldn't have thougfht about changing the tailight units. Thanks for the advice