66 Mustang blows accessory fuse when ignition is turned on

[danford1]

I just bought a 66 Mustang project car. It has a fuse blowing problem. The 14 amp accessory fuses blows as soon as you turn on the ignition.
I found a lot of wiring diagrams that say the fuse (number 1) controls back up lights, radio, PRNDL light and turn signals. My turn signals work fine.
I don't have a radio, nor does the car have backup lights. I found the connector for the PRNDL light but it is unplugged and I can't see where it would go.
I want to isolate the circuits so I can find the short but haven't found a good starting point yet. The radio appears to be on circuit 140, black with red going to a yellow 3 way plug. I unplugged what was in the yellow connector but still have a short. There appears to be another wire hooked to the fuse but I can't find it on the wiring diagram.
Can you guys help me understand this? What else is hooked to the number 1 fuse?
Thanks
Dan

 

[dochawk]

"This isn't the subform you're looking for"



you're more likely to find someone who knows anything about that Carr in the classic subform.

[and I thought that all 66s had backup lights. If yours is missing them, might someone have modded and left a dangling wire?]

 

[Noobz347]

Moved to the Classic Forum.

 

[danford1]

Thanks for moving my thread.
OK, I have more info. Here is a picture of my fuse box turned on its side and the wires spread out. It clearly shows a second wire going to the accessory fuse. The Black-red wire is in all the diagrams. The White wire isn't in any diagram I found.
Where does this white wire go? I found wiring info on the internet showing all wire colors for 66 Mustang. There are only 4 white wires (35,58,95,806). I can find 35 white wire in the alternator to regulator circuit. 58 wire is in the wiper circuit from switch to wiper motor. I cannot find 95 or 806 wire on any diagram I found. Yet my fuse box clearly has a white wire going to it. I believe my white wire is shorted to ground somewhere but I need to know where it goes to unhook it and check for a short.

 

[WORTH]

If the white wire is NOT on the diagram it was probably added by a previous owner, the quickest way to figure out where it is going, is CUT IT OFF, and see what doesn't work. It may not be used at all. Why aggravate yourself? These cars are simple, don't make it complicated.

 

[danford1]

The White wire was not added by a previous owner. It is factory.
Just cut it? I hope I get the opportunity to work on your car so I can just cut things. I’m trying to solve this problem in a more professional manner. I simply want to see a wiring diagram that has this wire so I can trace it.
Thanks for your response but I’ll keep looking for another answer

 

[WORTH]

Well, I'm no amateur my friend, but the quickest way to figure it out is to cut the wire, yoou can splice it with soldier and a piece of heat shrink if you need it back. If you want to do it the hard way buy one of these, they do work but they can be a pain in the ass.
Amazon product ASIN B000RFLR0U
View: https://www.amazon.com/Tool-Aid-25100-Short-Tester/dp/B000RFLR0U/ref=sr_1_2?crid=1CBV5MMN5OVZB&keywords=short+circuit+tester&qid=1684618308&sprefix=short+circuit+tester%2Cspecialty-aps%2C124&sr=8-2

 

[Noobz347]

I wouldn't cut it either. You can test wires without hacking them out of the harness.

 

[danford1]

I didn’t cut any wires. I cut the tape and unwrapped a portion of the harness above the fuse box.
The white wire was a pigtail with a female end. From research it was for dealer installed options but for an unknown reason isn’t on wiring diagrams.
Someone had a pale yellow wire plugged into it which went to the fuel level sensor in the trunk. That would be a short to ground. I also found other things plugged into the wrong places. It was a pain but I think I have it sorted.
Thanks for the help.