Trailer running light relay
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From: Bristol, TN.
Steve
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I have traced the running light wire from the fuse box to the trailer plug except what i couldnt get to behind the fuel tank and could not find anything wrong with it. I replaced the trailer plug on the back of the truck and that didnt work. I have a prodidgy brake controller that I sometimes wonder if it is working right. I cant seem to ever manually lock up the brakes on two of the trailers I pull. I turn the power up all the way on the controller and it dont seem to change the way the brakes feel. Is there any way a brake controller could be back feeding and blowing the fuse on the running lights. The other day I took the travel trailer down the road trying to adjust the brakes playing with the brake controller and by the time I got home the fuse was blown.
Hotshot
Joined: Jan 2010
Posts: 10,060
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From: Bristol, TN.
I have traced the running light wire from the fuse box to the trailer plug except what i couldnt get to behind the fuel tank and could not find anything wrong with it. I replaced the trailer plug on the back of the truck and that didnt work. I have a prodidgy brake controller that I sometimes wonder if it is working right. I cant seem to ever manually lock up the brakes on two of the trailers I pull. I turn the power up all the way on the controller and it dont seem to change the way the brakes feel. Is there any way a brake controller could be back feeding and blowing the fuse on the running lights. The other day I took the travel trailer down the road trying to adjust the brakes playing with the brake controller and by the time I got home the fuse was blown.
Couple of thoughts. First, if the fuse only blows when a trailer is hitched, the problem is in the trailer or the connection to the trailer. Can you make the fuse blow without a trailer being hitched?
Being able to lock brakes depends on brakes that are properly adjusted as well as the brake controller.
With an accelerometer brake controller, it is almost impossible to feel the action while braking as it matches the rate at which the truck is slowing.
I am guessing it is possible for a brake controller to blow fuses, although I have never personally seen it happen.
In my experience, most problems are the result of the interface between truck and trailer, although there are surely exceptions.
Steve
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I have a 19 foot enclosed snowmobile trailer and a 29 foot Dutchmen travel trailer and it seems to happen with both. In July I pulled the tt over 100 miles before the fuse blew. It seems the fuse will sometimes blow without a trailer attached. It is hard to pinpoint when the fuse blows because you don't realize it till you are hooked up and checking the lights to go down the highway. It just seems odd the other day when I went 2 miles down the road playing with the brake controller that the fuse blew that quick. Is there anyway a brake controller can be tested for proper operation? I keep thinking I have a bad wire. But I have searched everywhere. I have shaken the wire harness and wiggled wires with the lights on and can't get the fuse to blow.
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From: Bristol, TN.
Intermittent problems can be absolutely maddening. My thought is the fuse blowing is a random event simply correlated in time with other events. it is extremely easy to tell if a controller is working. When the controller is manually activated, you should see 10-12 amps with a clam-on meter around the the hot lead to the brakes.
Steve
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Thanks Steve, I will check that controller next. I still don't believe that is it. But I am looking for something easy before I drop the fuel tank and pull the whole wire harness out. I was thinking if there was a relay that was faulty that could be the problem.
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Hotshot
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From: Bristol, TN.
If it is the controller with an intermittent short, you should be able to duplicate the problem just sitting in the truck and activating the controller manually.
Good luck,
Steve
Good luck,
Steve
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From: South Shore, MA
You're not alone;
My 02 seems to blow the trailer running light fuse as well.
Sometimes I get an hour down the road before it blows, other times it's as soon as I turn the running lights on (even unlocking the doors with the remote can spit the fuse).
Funny thing is that; once it's blown, it immediately blowns again when I install a fresh one. BUUTTTT, sometimes if I go a few days or whatever between tows, I'll be able to get that hour or so ride trouble-free before it acts up again.
I don't have a trailer brake set-up at all -- So I can clearly rule that out of the equation.
Oh, and this is with several different trailers.
My 02 seems to blow the trailer running light fuse as well.
Sometimes I get an hour down the road before it blows, other times it's as soon as I turn the running lights on (even unlocking the doors with the remote can spit the fuse).
Funny thing is that; once it's blown, it immediately blowns again when I install a fresh one. BUUTTTT, sometimes if I go a few days or whatever between tows, I'll be able to get that hour or so ride trouble-free before it acts up again.
I don't have a trailer brake set-up at all -- So I can clearly rule that out of the equation.
Oh, and this is with several different trailers.
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From: Pflugerville, tx
I blew one as well, on my second tow with this trailer..
replaced fuse and towed 50 times since then, once for 10 days and have never had a problem..
I did reseat all the wires in the trailer connector in between those events.. as it seemed the trailer side wire wasn't secured as much as I like..
sam
replaced fuse and towed 50 times since then, once for 10 days and have never had a problem..
I did reseat all the wires in the trailer connector in between those events.. as it seemed the trailer side wire wasn't secured as much as I like..
sam
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Today I blew the fuse and it was not plugged into a trailer. I've been trying to monitor it with a 4way plug in tester that I keep plugged in all the time. I pulled the dash apart and still can't find any loose or bare wires. I wonder if a bad light switch or relay could cause this. Is there a trailer running light relay on a 2007 f350?
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From: Pflugerville, tx
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