This is my first post here, I hope someone can help me out. I have a 2002 F150 XLT that I installed a hitch on but it was prewired with a 4 flat pin connector. I have pulled several trailers but now have a problem. When hooked up to my ATV trialer, the brake lights on the trailer dont work and with the blinker on, both trailer lights flash. I hooked the trailer up to another truck and they work fine. Does anyone have any suggestions? Thanks.

 

Your 4 pin connector on your truck is miswired.

 

I have used it in the past with no problems, and have not touched the wiring from the factory.

 

Sounds like a bad ground on the trailer end.
Trace the white wire, more than likely headed toward a rusty bolt on the body of the trailer.

Just clean it up.

If both ends are clean, it may be crimped somewhere along the way.
If not there, examine both plugs.
The four pin plugs are designed in a 3+1 configuration so they can only be put together one way.
The pin that is 'different' on both, is the Ground pin, examine that.
Your symptoms are a ground problem, I'm pretty sure.

 

If that were the case, why would the trailer lights work correctly connected to a different truck?

 

Bad ground is a tricky thing.

 

I will try the ground on the trailer tonight and see what happens. I also have another trailer that I can try and see if the lights work on it. I hate electrical problems!

 

Raoul

Should be correct...it is probably the ground. These computer controlled cars do weird things when electricity flows in a dirrection it is not supposed to.

If you follow the ground wire up from the rear bumber it will be screwed into the frame with a self tapping screw....it could be loose or corroded.....or...more commonly the ground on the trailer has broken off or was never connected.

It is so common in trailers that when I rewire trailers I will install 2-3 grounds to trailer frame to make sure it will continue to work...even if one gets broken. (one near trailer brake, at nose of trailer and again near the rear tail lights)