Hi all,
I need help big time. My dad has an old 1986 Ford F150 4x4 auto tranny with the 302 5.0L and he has been blowing fuses faster than he burns up gasoline. The fuse that keeps on blowing is the lighter and horn lighter. Now he doesen't have the horn cover it is just a bare wire that he taps agianst some metal and it does it's job but it has been like that for years and no problems. We looked for any melted wires or anything and found one which went from the door speakers to the new speakers mounted behind the seats. He has been putting in 20 amp fuses which what it calls for it and it blows he also has tried bigger and smaller and still. I can't find any signs of something shorting out. We are tired of replacing fuses. Nothing has been changed on the truck other than that horn cover could that be the reason? I am not sure I am not to good with these 86s I am better with my 88. Thanks
Trav

 

The horn wiring is part of the turn signal switch and I would investigate there (by removing the steering wheel and looking for bare/rubbing/shorted wires).

There are two spring-loaded contacts for the horn button protruding from the switch assembly that contact specific areas of the steering wheel; also, the wiring for the emergency flasher switch is directly below the installed steering wheel, rubbing & abrasion from incorrectly-installed components can cause problems.

You could also unplug the wire from the back of the lighter's socket, that will eliminate the lighter assembly as the cause.

A penny or similar-sized piece of metal inserted into there will cause a short circuit.

 

I just happen to be a mechanic, btw. Not an expert in ford trucks. but an expert in many things to do with troubleshooting electric.

Ok I got a few things for you to test.... or check. First lets start with a few things. Tapping the bare wire for the horn on bare metal will never make the fuse blow. (without any other problems) This is effectively what you are doing when you press a regular horn button.

Here are a few things to remember, This helps me with wireing problems.
1. if something electric not working when requested (turn on a switch) you have an open circut.
Either on the hot wire or the ground wire, could be before or after a switch
2. if you have something working when not demanded, like if you turn on the light switch, and the wipers turn on, you have a "short to power" keep in mind this can happen also when the ignition switch is turned on. This is rare but it happened to me just the other day on a Freightliner, won a heated debate with a coworker over this

3. Here is the most useful rule. "Fuses blowing" means you have a "short to ground."
NEVER NEVER NEVER!!!!! increase the fuse capasity, or wrap a fuse in tin foil, or put a bolt in place of a fuse unless its "life or death" situation And loosing the vehicle is worth the risk. Ok back on track, It is important to note what action is done immediately before the fuse is blown. This will help you track it down.
The bottom line is I know you got chaffed wires somewhere, you just got to track em down, and a clue!!! they wont be in the door speakers

Mark

 

i had the next steps typed out and then internet went down, so i lost it all! Just pm me and I will talk you through it....

And BTW the reason you should never increase a fuse capasity is because you can start the wireing on fire and burn the truck to the ground I have seen it happen... never a good day

 

Hello ctubutis,
I checked that already forgottomention that and nothing wrong with those wires. I just replaced the cigeratte lighter spot because it wasn't working right. I checked that yesterday and two hours later I am replacing the fuse again. thanks for your attempted help though. Oh and most of everything is off of the steering wheel because it was ruined by the last owners and you can see straight through the middle of the steering wheel and look staight down the coulum.
Thanks,
Trav

 

Have you checked the cigarette lighter? In the old days it was only used by smokers, but now it's used by all kinds of accessories for power, and people do plug in stuff they are not supposed to and the socket can melt or fall apart.

 

OK, let me ask....

Does a new fuse blow when the ignition is OFF and nothing (to your knowledge) should be turned on?

How much time elapses between fuse replacement and it blowing? What electrical activities (ignition turned on, wipers turned on, etc.) take place during that time?

The horn & lighter always have power regardless of the key position but having the key OFF helps narrow things down (in an unmolested wiring system).

Did this problem begin after replacing that lighter socket?

If so, that suggest an incorrect installation or similar wiring problem at that location.

I would electrically disconnect the lighter socket *as well as* the half-moon-shaped turn signal switch connector under the dash and then see what happens.

That will keep the horn & turn/emergency signals from working but it'll help you narrow down where the problem is.

If that results in the fuse no longer blowing, plug in one of those two again and see what happens.

As was explained above, a "short to ground" can cause real problems, including electrical fires.

 

Hey Franklin2,
I have replaced it with a brand new one set up to be able to plug in everything from cell phones to cigeratte lighter and even them portable dvd players (even though we don't use them)
Trav

 

Hey,
Yes it does sometimes blow when everything is off but usually not. Yes it started after I put a new one in and I already checked if those wires are wrong and again still blowing (first thing I did check.) I will check those other things tommorow (or later depending on how it goes with changing the shocks on my 1988 F150)
Trav

 

What you could do is put the old lighter socket back and see if your problem goes away; if it does, there is a problem either in the wiring or with that new socket.

 

Okay I will check that too along with what PA-Mark said. Thanks.
Trav

 

Hey yall,
This truck use to have a roll bar with KC Lights on the roll bar and this caused the problem:
You aren't going to believe this but the last owner or whoever took of the KC Lights went and connected two hot wires together causing them to short out because of the fact that they were hard wired into the cigerratte lighter. Man sometimes I swear. I got everything dandy as can be now Thanks for the help I would have never spotted that.
Trav