2006 Ford Expedition V8 Four Wheel Drive Automatic 41,000 miles
I recently took possesion of my fathers old 5X10 utility trailer. It needed new lighting so I stripped off the lights and the old wireing harness. I've purchased three new light kits and continue to have the same problem. I wired the trailer as per the directions supplied with the kit. When I plug in the four prong plug into the back of my vehicle the tail lights work, the turn signals work, and the four ways work. But when I step on the brakes the tail lights go out. I called the technical phone number on the last kit I bought and the answer I got was that I needed a " relay" in my vehicle. What kind of " rely" and where would it go? Can I just rewire the light kit?
Actually, it sounds like there is a bad ground. Check and make sure the ground on the vehicle is good and clean. Also, with a test light, make sure you have the correct wire from the vehicle going to the correct wire on the trailer. If you are not sure of the wire on the trailer, use a battery charger to supply power to each pin until you find the correct one for the brakes. As far as a relay, I wired a lot of trailers over the years (infact I have an Expedition in my driveway that is wired for a camper and a small trailer) and never had a brake light relay, whatever that is.
Let me know what you find.
November, 11, 2009 AT 3:42 AM
You are correct. It was a bad ground. This trailer is a tilt trailer. While I was working on the problem, and old friend showed up, (a retired Master Chief Engineer from the Coast Guard, I was CG too) and asked me for a peice of wire. He touched the back of the light to the front of the trailer and said try it now. It worked! He explained that the pivot point on the trailer did not properly allow for a good ground. All I had to do was run an extra ground wire forward and problem solved.