Trailer wiring issue...

[Stratosman]

I have never owned a trailer that I didn't have wiring/lighting issues....anyway.

What's this a bad plug or what? Lights are kinda dim and running lights are as well. And when I apply the brake, the brake lights don't work and the running lights go out....The blinkers work, so....is it a bad connection, bad RV plug or something else....Man I hate trailer lights...

[hydro]

Sorry to say this, but you have a bad ground connection somewhere between the body of your vehicle and the back of the trailer. Your symptom is caused by the dual filament common ground in the run/brake light bulbs. The first thing to try is a wire between the vehicle and the trailer, both ends alligator clipped to bare metal and see if the problem goes away. If it does, clean and re-ground the white wire on both sides of the connector.

If the problem is still there start tracing the ground circuit back to the lights.

[hydro]

Here is a trick that I have used successfully. Take some 16ga or 18ga white wire and run it to each tail light assembly's ground wire termination, then up to the ground point where the harness's white wire terminates on the tongue. Try to make direct contact to the ground wires at each point, not just to the frame. That bypasses all of the trailer frame bad ground issues with good old wire.

[Stratosman]

Thanks alot for the advice....I'll give er a try!

[marine_man]

It's definitely a ground problem.

Check your trailer connection at the plug as well. Is the white wire coming from the trailer's plug grounded anywhere? If not I'd add a screw grounding that wire to the trailer frame.

Then, follow the white wire from the tow vehicle's plug... is that grounded out somewhere?

marine_man

[Stratosman]

The only place the white wires on the trailer are grounded are at the tail lights. And I don't see a ground wire coming out of the RV style plug under my truck... It has always worked until the last time out. I still havn't tried jumping with straight wire between truck and trailer yet though.

[LindellProStaf]

The bolts that hold the tail lights on sometimes get rusty and lose the ground. Try touching a wire from the taillight mounting bolt to the frame of the trailer. I had to put a short jumper on my trailer there once to ground the taillight on one side.

[marine_man]

I still havn't tried jumping with straight wire between truck and trailer yet though.

Give that a try. If that works, ground the trailer side plug to the tongue somewhere and see if that resolves the problem.

Lindell's post above is good advice as well.

marine_man