Electrical Fuse 8, Light Green / Black Wire

bleedinggreen · Jun 23, 2025

I have an 89 Mustang that I'm in the process of installing AC in. While I have the dash out, I'm cleaning up the wiring harness a bit. I have a light green / black wire coming off of the fuse box (fuse 8) that I can't find in any wiring diagram. There is a light green / black wire on the driver side footwell courtesy lamp that is the ground for that lamp, but none of the courtesy lamp wiring on either side looks factory. On fuse 8, there's a light green / yellow wire on one side and the capped light green / black wire on the other. Can anyone help me identify the light green / black wire on fuse 8?

85GTStangGuy · Jun 23, 2025

Would these be of any help?

Pardon Our Interruption...

bleedinggreen · Jun 23, 2025

85GTStangGuy said:
Would these be of any help?

Pardon Our Interruption...

Possibly. I sent them a message to see which diagrams are included. They look pretty nice, so I may get them regardless, along with a set for my Harley.

AeroCoupe · Jun 23, 2025

That wiring on the curtesy light is by no means good so that should be addressed. If memory serves me right the curtesy light ground through the metal body so I don’t think that is a factory light. It’s been yeeeears since I’ve had the dash apart on mine so probably need someone else to chime in.

bleedinggreen · Jun 24, 2025

AeroCoupe said:
That wiring on the curtesy light is by no means good so that should be addressed. If memory serves me right the curtesy light ground through the metal body so I don’t think that is a factory light. It’s been yeeeears since I’ve had the dash apart on mine so probably need someone else to chime in.

I'm going to be removing the courtesy lights from each side as neither one looked like it was wired correctly. The thing that is messing me up is the capped off light green / black wire that is coming out of fuse 8 and the light green / black wire used on the courtesy light is the same. I'm not sure if that originally came out of the fuse and went somewhere else. I can't find it on any diagrams. I've looked through everything on Very Useful, Charm.li, and my Haynes manual.

AeroCoupe · Jun 24, 2025

If you get a copy of the original wiring diagrams for the car and fuse #8 has a different color wire or no wire at all I would say the previous owner(s) added it.

Noobz347 · Jun 25, 2025

LT Grn/Yel is the feed wire for the mirrors, left and right.

It also feeds the filler door release, door switches, and the vanity lights.

There is a blue/black wire that runs between these components and ground but no Green/Black.

Somebody must have previously stolen that fuse to feed power for something else.

bleedinggreen · Jun 26, 2025

Noobz347 said:
LT Grn/Yel is the feed wire for the mirrors, left and right.

It also feeds the filler door release, door switches, and the vanity lights.

There is a blue/black wire that runs between these components and ground but no Green/Black.

Somebody must have previously stolen that fuse to feed power for something else.

Thank you for the info! I guess I'll remove that green/black from the back of the fuse then. I appreciate the help.

Electrical Fuse 8, Light Green / Black Wire

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Electrical Fuse 8, Light Green / Black Wire

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