Trailer light problem

[55belair]

I put a complete new light harness and new trailer lights on my dad's boat trailer last night. Here's my problem. With the headlights off, everything works fine, but when you turn on the headlights on, both trailer lights flash with either turn signal and they go off completely when you hit the brakes. It's a galvanized trailer so my first thought was bad ground, so I connected the white trailer ground directly to the truck ground to eliminate that but it still does it. I also checked the plug on the truck with a meter and everything there is fine, 12V at all three prongs with tail lights on and brakes applied. Then I checked the wires at the lights and everything loses power when you hit the brakes. The lights say that they are self grounding, but they have plastic housings so I don't see how they could ground, plus I don't understand why that would affect the voltage through the harness anyway since it's basically just a 18' extension of the truck harness. Any ideas?




Modified by 55belair at 8:41 AM 5/23/2008

[Tritonbmc]

ttt

[Fish TR19]

On my old trailer the lights grounded through the bolts that held the light housing to the trailer. Maybe you are not getting a good ground there. I think the white wire on the trailer plug would need to be connected to the trailer and the white wire on the truck plug connected to the truck.
It sounds like a bad ground to me.

you could try clipping long wire to the bolt that holds the light on and run it all the way to the front just to test it.
I am not sure but I think only one of the bolts for each light was the ground. I had a metal contact inside the housing. Good luck

[55belair]

I finally figured it out. It was not getting ground at any of the lights. I guess since it's galvanized the ground does not conduct very well through the trailer itself even though I removed all the coating from of the light mounting brackets. I ended up having to ground each light separately with pig tails to the trailer frame. Between the tail lights, the harness, and the marker lights it now has 6 separate grounds. What a pain in the azz!