Perplexing brake light issue.
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Senior User
Joined: Apr 2000
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From: Minnesota
Perplexing brake light issue.
The brakes lights on my 1986 F-350 Dually with cruise stay on for some unknown reason.
I have swapped steering columns and unplugged the y harness for the cruise since it had bare wires.
I have also unplugged the brake light switch.
With the brake light switch unplugged and the column unplugged, both sides of the brake lights switch are still hot with my test light.
Is there something else in the circuit that I am missing? Or is there a short in the main wiring harness?
I have swapped steering columns and unplugged the y harness for the cruise since it had bare wires.
I have also unplugged the brake light switch.
With the brake light switch unplugged and the column unplugged, both sides of the brake lights switch are still hot with my test light.
Is there something else in the circuit that I am missing? Or is there a short in the main wiring harness?
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Senior User
Joined: Apr 2000
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From: Minnesota
I just got done tearing 2/3rds of the dash apart. Found out that the wires in the harness for the brake light switch melted and fused together. the one wire also glued itself to other wires in other locations.
Why this happened is the big question.
I have owned the truck for about three years. At that time I ran all new trailer brake wiring and 7 blade RV plug. About two months ago, I modified the rear wiring. I removed the Hoppy wiring T and replaced it with my own T using the new style plug the superdutys are using. This allowed me to plug in a T so I can use two RV plugs. One for my car trailer and the other for the slide in pickup camper. The only problem I have had with that is that the AUX wire keeps blowing a fuse.
Should i replace this section of harness with new wire? Or replace it with a junkyard section? Or replace the entire truck harness?
Why this happened is the big question.
I have owned the truck for about three years. At that time I ran all new trailer brake wiring and 7 blade RV plug. About two months ago, I modified the rear wiring. I removed the Hoppy wiring T and replaced it with my own T using the new style plug the superdutys are using. This allowed me to plug in a T so I can use two RV plugs. One for my car trailer and the other for the slide in pickup camper. The only problem I have had with that is that the AUX wire keeps blowing a fuse.
Should i replace this section of harness with new wire? Or replace it with a junkyard section? Or replace the entire truck harness?
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Joined: Nov 2007
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From: Denver Metro Area, CO
I would replace the melted wires.
A fuse of the proper rating is supposed to prevent exactly that from happening, do you have the proper size fuse installed for the brake lights?
I don't know enough about trailer wiring to know what an AUX wire is or what circuit it'd be hooked to.
A fuse of the proper rating is supposed to prevent exactly that from happening, do you have the proper size fuse installed for the brake lights?
I don't know enough about trailer wiring to know what an AUX wire is or what circuit it'd be hooked to.
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Senior User
Joined: Apr 2000
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From: Minnesota
What are the correct fuse sizes and locations for this truck.
The previous owner had 30 amp fuses in several locations that I don't think are correct.
The AUX is for charging the camper or trailer battery along with providing power for lights in the camper.
The previous owner had 30 amp fuses in several locations that I don't think are correct.
The AUX is for charging the camper or trailer battery along with providing power for lights in the camper.
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Joined: Apr 2011
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From: Tri-Cities
You ~might~ be asking for too much current through the size of wire that was originally there. If you go new, go bigger as far back towards the alternator as you can, and then size the fuse to the total demand the circuit will have with a trailer attached. Cultivate a Journeyman Electrician if you can. Beer often works well for that. 
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