I just bought a trailer and trying to get the trailer lights to work right. Towing with an 02 suburban. When I have my headlights on the lights on my trailer seem fine. However, with the headlights on, when I press the brake my brake lights on the trailer turn completely off. All of the running lights stay on. With the headlights off when I press the brake the brake lights on the trailer work. Any suggestions???? I tried changing the wires around and it still does the same thing.
Thanks,
Jon

 

Good luck with rewiring it

 

Have you installed a module that will go from a 5 wire system that your suburban has, to a 4 wire system that your trailor has(if it is a 4 wire system).
something like this http://www.etrailer.com/pc-VWH~118175.htm

When applying the brakes with the lights off, are they bright like brake lights should be?...or are they the same brightness as the parking lights are? if so, check to make sure the wires are run properly to each light.

 

any luck with it yet? I am having the same exact problem with my 97 silverado. I just put new wiring on my trailer since the old ones were all corroded. I already replaced the plug on the truck with no luck. Re-did the ground wire as well with no luck. Still cant figure out what it is.

 

question does this have a factory plug on it ? if you put a different plug sounds like there are some wires hanging out of the plug where they are installed from the running light function the touching the brake lite pin,if factory 7 wire check for corrision in the plug under the lift up door,disconnect the wire connector from the plug ,check ther also sounds like voltage crossing over .