Pop up trailer lighting

[motorboatinking]

I have a 1996 Jayco Eagle 8. It has a 6 square plug harness, and my tow vehicle has a 4 way flat. I got an adapter, and it doesn't quite work right. The brake lights do not work when the headlights are on. If I turn the headlights off, the brake lights then work like normal. Turn signals work fine. I just don't know what would cause the brake lights to not work only when the headlights are on.

 

[Unolocogringo]

Need more info.
Tow vehicle?
Factory wiring on tow vehicle?

 

[motorboatinking]

2013 outback. And factory wiring. The harness plugged into an existing plug in the out back. Using a multimeter the vehicles harness is operating correctly.

 

[Unolocogringo]

After a little looking around it appears the Outback uses separate lights and circuits for Driving,Turn and brake lights.
The trailer uses two circuits.
One for Marker lights when the headlights are on and the other is a common circuit for brake and blinker.
So it appears you will need an adaptor for proper operation.
Unless you are technically inclined I would suggest taking it to a trailer hitch installer and have them install the correct adaptor and plug to match the one on the camper. otherwise you will need 2 separate adaptors which are not guaranteed to work together properly.

 

[motorboatinking]

Someone on another forum said for trouble shooting to run a wire straight from the negative terminal on the trailers battery to the negative on the brake lights. When I did this the brake lights worked at the same time as the headlights. So that would mean the ground somehow isn't working when the headlights are on. Could I just run a new wire from the lights and mount it on a bolt on the trailer frame so it has a new ground?

Attaching a picture of the brake lights. The running lights are a different type of bulb and the are above the brake lights and go all the way around the trailer.

 

[motorboatinking]

I ran a screw from the bottom left screw of the brake light to a bolt on the frame and everything works now.