Electrical Hi all! New here! Hoping to get a little help with a problem i am having on my 93 Foxbody!

iGOON

New Member
Feb 1, 2020
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Hey guys and gals. I'm having a fuse problem on the fox. Fuse #8 keeps blowing. It blows out as soon as the prongs touch in the fuse box. I can put a bigger fuse in it, (20a 25a) and it will hold untill I crank the car, (turn the engine over) then the bigger fuse will blow. Thought I might be the ignition switch, so I disconnected it from the harness and tried to put in a fuse and it still wanted to blow. Now i know fuse #8 is a constant hot, but should it be even with the ignition switch unplugged? Any help would be great. Thanks.
 
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kiddiccarus

The first widely accepted Tranny
10 Year Member
Title: 1993 Fox
Section: 5.0

mustang-5.0-fusebox-wiring-diagram.gif


OK, 1993 5.0

#8 is a 15 amp and runs Courtesy Lamps, Dimmer Switch, Power Mirrors, Radio, Fuel Filter, Door Release, Etc......

Did you alter, replace, bump, destroy, upgrade, or CUT anything prior to this issue?
 

iGOON

New Member
Feb 1, 2020
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This has been going on for a few months now. I have replaced the radio and headliner since the issue, but didnt notice till i replaced the radio. The radio worked fine for a few weeks before the problem occurred. I unplugged both the radio and dome light from the harness and still wants to blow a fuse.
 

kiddiccarus

The first widely accepted Tranny
10 Year Member
Go back into the radio harness. Check for any exposed wire that can be causing a short and also re check that ground. I have had a situation in my old Fox where a wire began to touch a piece that was grounded. I didn't notice it for a few months after installing the radio. That is why i never checked it. Somehow over time the harness settled and the exposed wire came into contact with something grounded and I began blowing fuses at an alarming rate. It was frustrating because this would change for me after driving, somehow that wire would get away from the part it was contacting for a few days and then go back. I can only imagine it was because of the way I drive and that harness rolling with inertia.
 

iGOON

New Member
Feb 1, 2020
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I have an aftermarket connect for the radio sp I didnt have to cut into the original harness. But with the radio and harness completely out of the car, wouldnt that eliminate the radio? Unless its in the original harness. And im still confused about it trying to blow with the ignition switch unhooked. Doesnt that remove the constant hot from fuse 8? Sorry. Im a noob when it comes to electrical.
 

Blown88GT

Founding Member
Nov 13, 1999
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Palm Beach Gardens, FL
I've had #8 do some strange things. Blow for absolutely no reason on 2 occasions, then never again.
Every one is a noob at some point. I am not. 2 degrees in electrical engineering & this stuff can still drive me crazy.
The only way to find it is if it keeps blowing. They make some basic test equipment that will zero in where the short circuit is located. Bought one a couple years ago: Automotive Short Open Repair Tester Tool Finder Cable Circuit Car Wire Tracker

Did buy a 15A circuit breaker just for testing.
 

iGOON

New Member
Feb 1, 2020
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I did not know they made a tool like this. Short finder. I just looked and I can get one from Harbor Freight. Same price. So i guess im going wire tracing. Thank you for all your help.
 

dgollem

Active Member
May 5, 2004
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Waldorf MD
Also another thougt since you said you changed your headliner and the courtey lights are on the circuit could there be a pinched or worn wire to the dome and or maplight. Or sun visor vanity mirrors if they have lights. Good luck
 

iGOON

New Member
Feb 1, 2020
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I did not think about the sun visor vanity light. Ill have to check that out. It is by the screws holding my headliner. And all things on that circuit seems to not be working. Im going to get a few tools next weekend and do some wire tracing.
 

Blown88GT

Founding Member
Nov 13, 1999
1,854
392
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Palm Beach Gardens, FL
I did not know they made a tool like this. Short finder. I just looked and I can get one from Harbor Freight. Same price. So i guess im going wire tracing. Thank you for all your help.
Is this the HF one?

or this one?
 
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Blown88GT

Founding Member
Nov 13, 1999
1,854
392
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Palm Beach Gardens, FL
When I was working, we had a professional version of one those (about $200). Could never get it to work on live electrical power circuits, even though the tone generator was an AC plug.
Regarding the HF version, one reviewing said "Does not detect signal more than a few inches away."
That was my experience with the pro version. The HF tone generator won't work on live AC circuits.

BTW, the Cen-Tech unit is almost identical to the Extech TG20.
Extech is pretty good quality.

Found this; good explanation on how to use it (scroll down).

After listening to the video, he said a tone generator is different from a circuit tracer, which is confusing because a tone generator is a circuit tracer.

This is going to be difficult, if not impossible, to find a short circuit in a cable bundle.
If it doesn't work, then....
I think this is a better tool for this application because it has an automatic resettable circuit breaker.
 
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