On my 86, I keep blowing the fuses for the brake lights and the turn signals.......but I dont even know where to start looking.........This is gonna be fun....

 

You happen to be in the 1973-1979 forum.

What I would do is disconect your rear harness, (The harness going to your taillights and license lamps etc) at the plug off of the frame rail harness that goes down the left frame rail of the truck.

Remove the rear harness from the truck, Unwrap the black plastic wrap covering the wires and inspect the wires for cuts, abrations etc, fix any problems you discover, and rewrap with black electrical tape.

Do the same with the Frame rail harness, disconnect it at both ends, and at the various plugs down the frame rail, and unwrap it as before. Fix any problems and then re-wrap with electrical tape.

What happens over the years is that the frame rail harness can rub on the frame, or get snagged by crap.


hope this helps,

 

Do you have a trailer light plug installed? Trailer wiring problems can cause all kinds of wierd problems.like blowing fuses,Brake lights on when parking lights are on,parking lights flash with turn signals.and so on.You can do as above and disconnect the rear light harness on the drivers side behind the bumper.Then replace the fuse and try everthing.If it doesnt blow it has to be trailer plug or rear light problems.


Tim

 

I saw this post and my problem might be related.... What do you think?

I have an 84 F250 dually. For some reason, on occassion, when I operate the heater controls, it blows the fuse for the tail and dash lamp. This happens every once in awhile only. I have dissected the entire dash and have found nothing. I can only assume its in the control mechanism? Have you ever run across this?

I used to have an 84 Bronco that had the exact same problem. I was surprised to not see any postings on this.

- Ken

 

81 F-150 Explorer is definetly on the right track, it's probably closer to the tailight side of the harness. More than likely it's a short to ground but I'd say before you go through the trouble of removing the wiring and inspecting it all, simply remove the screws that hold the tailight assembly in place and pull the whole thing out. Then, put a fresh fuse in and have someone step on the brakes and activate the turn signals while you jiggle the wiring and move it to different places. See if this makes it happen more/go away. If it seems to do it more or less in certain positions then that would suggest that you are breaking/making the shorted path to ground. Also, does this happen on both sides or just one or better yet, are there seperate fuses for the turn signal and the brake light or do they share a fuse? Does this happen just on one side or both sides of the truck?

 

Hi Ken -- Here's my experience w/ my 85 f-250. I could get brake lights to work, or turn signal, but everytime I'd replace a brake fuse it would be blown in minutes. Finally figured out I couldn't get brakes and signal together. After rewiring rear lights numerous times and ways -- including flat 4-prong trailer connection -- and checking for weeks I finally replaced the turn signal wiring harness (flasher, etc in same unit) in the steering column and eliminated the mystery short. The unit includes turn signal cancellation mechanism and about a dozen wires in a plug-in module. It involves using a wheel puller and some disassembly of turn signal cancellor. The harness plugs in down the steering column in a semi-circular connector. The biggest hassle was re-fitting the keyed ignition unit so that it worked correctly -- involved a long skinny metal shaft to release ... (can't recall what, but it had to be reconnected correctly). Cost of new turn signal unit was around $65 -- several hours out and back in. Hope that help -- Garcia

 

thanks, I appreciate it. Ireplaced the brake fuse only and so far it is working