Posted 2007-04-14 9:25 AM (#59273) Subject: F350 & Trailer brake issues...turn on lights, brake engage
New User
Posts: 1
Location: Fries, VA
On my F350, when I turn on my lights my trailer brakes kick on. I researched and found, actually had to purchase some info on wiring diagrams...some help, but not much. I recently had the brakes to lock up.
Here is what I have done: checked all fuses and relays, trailer plug. I know that I have a grounding problem....but it is a mystery to me where. I know that when the lights kick on, that the brakes are grounding and engaging.....
Posted 2007-04-14 9:55 AM (#59277 - in reply to #59273) Subject: RE: F350 & Trailer brake issues...turn on lights, brake engage
Member
Posts: 22
Location: West virginia
I had the same problem on my truck after i had a new bw turnover hitch and brake controller installed.they used the wrong wiring harness from the brake controller,to the fusebox.my truck has a sensor that turns the lights on automaticly,not good to have your brakes lock up going down the road at 55 mph. luckly i didn't have my horses loaded.check to see if your factory harness was used mine was still in the glovebox.they switched harness and i've had no problems after that.
Posted 2007-04-14 1:01 PM (#59280 - in reply to #59273) Subject: RE: F350 & Trailer brake issues...turn on lights, brake engage
Extreme Veteran
Posts: 500 Location: West TN
I encountered a similar instance a few years ago with a fellow teacher that we hauled with to FFA livestock shows. On our way back one of the women that hauls had the problem that when she went to turn on her lights at night, her trailer locked up. We ended up realizing that one of the kids had pulled the break away cable off the emergency brake box. I guess the battery on this was dead and when we turned on the lights, it was causing the problem. It took us a very long time to make this discovery. We initially checked all the connections and wires, but this was the one thing that did the trick for us. Once we put the plug back in all was fine. Of course, your situation could be completely different.
Posted 2007-04-14 1:28 PM (#59281 - in reply to #59273) Subject: RE: F350 & Trailer brake issues...turn on lights, brake engage
Extreme Veteran
Posts: 304
Here's a shot in the dark (no pun intended) but a lot of wierd things happen on certain year Ford Trucks when the 3rd brake light burns out(the one on the back of cab) Have you checked it yet? You might be lucky and just have a burned out bulb. It has fixed many of electrical gremlins before.
Posted 2007-04-14 9:53 PM (#59303 - in reply to #59273) Subject: RE: F350 & Trailer brake issues...turn on lights, brake engage
Veteran
Posts: 143 Location: southeast U.S.A.
2feathers,
Just a couple of possibilties to check out.
Your trouble is not a grounding problem but that the trailer brakes are being fed voltage in some way from the light circuit. Look for a frayed wire in the plug that plugs into the truck from the trailer,this wire could have completly come loose or just a strand or two rubbing the terminal that feeds the brakes. Also , if this is a new instalation,recheck that the wires for the brakes and the lights are not crossed. The next think to check is some controllers have instrument lighting and this may be wired into the brake curcuit.let us know if this don't solve it and I'll try to think of more possibilities.
F350 & Trailer brake issues...turn on lights, brake engage
luckly i didn't have my horses loaded.check to see if your factory harness was used mine was still in the glovebox.they switched harness and i've had no problems after that.
