blowing number 8 fuse

[typ4]

I am blowing this fuse all of a sudden , the guide says courtesy lights and warning buzzer, It also is radio memory. I dont have a wiring diagram to see what else. Anyone have any ideas what else it runs? Checked all door switches and pulled dome and cargo bulbs, still blows.
Thanks
Russ

 

[tonkadoctor]

Checked all door switches and pulled dome and cargo bulbs, still blows.

You have a 99.99999999999999999% chance you have a bare spot somewhere that keeps touch or is touching bare metal.

If the load was fine before with the lights etc inplace, removing a few lights to lighten the load won't cure the problem.

Start at one end and trace the wiring to the other, it's the only way to find the short sometimes it takes 2 minutes to find and sometimes it might take 2 days to find. Electrical work bites IMHO

 

[typ4]

Gee thanks for telling me what I was hoping it wouldn't be. Anyway I figure it must be under the floor mats , nothing else has been disturbed. lucky for me I am very good at electrical, except for these damn bifocals,they don't mix with dash work too close, too far away, then they end up on the floor, know what I mean.
I removed the bulbs because once in my career I had a headlight filament holder short to the one below it and it took out the whole headlight harness, customer was mad , then I reminded him that he brought me the lights to put in, cooled him right off.
thanks tonka
russ

 

[tonkadoctor]

I feel your pain. I can't see a damn thing without my glasses anymore and if I get stuck twisted up under the dash the wifey has to get me out.

I had a short in my '93 plymouth duster that would knock out my dash lights whenever I had the lights on, had my foot on the brake pedal and then released the parking brake. Once I finally figured it was that combination I was able to find the wire with a bare spot right near the park brake assembly. Took about 2 months to finally find it and I'm not to bad with electrical work.

We always charged by the clock hour on electrical repair in the truck shop I worked in as you never knew what to expect.

I've heard of using a compass to find a short but never tried it myself, someone else may be able to explain an easier methed than eyes and hands.

 

[typ4]

I found a Haynes manual at the electric shop and that fuse runs the dome, cargo and glovebox lights, radio memory and warning buzzer?? That should narrow it down, I cant see the glovebox switch so I bet it fell down, zzzzttt, that would be easy..

I also charge by the hour on electric problems and yes it gets expensive some times. I did a motorhome once that someone had added wires instead of fixing the problem, ended up with a mountain of wire and then fixed the original fusebox, the fix took 30 minutes ,cutting out the crap about 3 hours, explain that to a customer sometime.

 

[tonkadoctor]

I also charge by the hour on electric problems and yes it gets expensive some times. I did a motorhome once that someone had added wires instead of fixing the problem, ended up with a mountain of wire and then fixed the original fusebox, the fix took 30 minutes ,cutting out the crap about 3 hours, explain that to a customer sometime.

Had a GMC General like that but prolly worse. The owner had tried to rewire everything under the dash gave up and brought this chopped up mess to us. Took me two days to rewire the entire truck and put the dash back in.

HE WAS PISSED when the boss handed him a bill for over $2k

 

[highest_vision]

I realize your truck has a manual transmission, but autos that have the OD switch in the gear shift use that fuse for power. Don't know the location of the switch in 91, if it could be in the shifter, the wiring may be there and may have rubbed.
You can also stick a headlight in place of the fuse and jiggle wires and once the headlight goes out, you have likely found the area of the short. Headlight creates sufficient load to not need a fuse but not so much to be a problem.
James

 

[typ4]

Highest vision, you know that is the best idea I have heard of. All these years of wrench spinnin and I never thought of that.
Thanks,I'll let you know what I find.
Russ

 

[typ4]

Used the headlite trick and found the wires going to the rear of the cab pinched under the seatbelt bolt, must talk to the daughters boyfriend about that ,he did the install. All works now And I think I can just mount the map, dome combo light I have in the same location the extra wire is there for the hot all the time map lights, gotta love Ford and the extra wires