Thanks for checking this out! About a week or two ago, I noticed that my A/C switch on the highest position would not work. So I thought that the switch crapped out, and replaced it. Same thing! It works on all the other settings, but not High. I checked the wires to the blower under the hood and they look okay. Any ideas!? Help!

 

ES,

I'm guessing that you mean the BLOWER doesn't work on the highest speed. If that is the case, the blower relay has likely failed. If all other blower speeds operate normally, you either have a failed relay, circuit breaker, or switch in the AC controls. Most likely, it's the relay itself. You can find it near the blower motor in the right side of the engine compartment:



The relay is at the left of the blower resistor in the photo.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Most likely, your problem is the same one as everybody else that has this happen to them...

In Vader's pic, you will notice a red and a black wire at the extreme right edge, next to the evap housing. The red wire supplies the hard battery to the high speed relay for the of the blower motor, which totally bypasses the resistors. (In fact you can remove the resistors from the car and high speed will work, unaffected. The relay is the little black bax with the white writing on it just below the resistors that the arrow is pointing to.) The red wire is part of the A'C wiring harness, and goes about 3" farther than what you can see in that pic, where it plugs into a similar red wire that's part of the chassis wiring harness. That connector is wasted. Unplug it and you'll instantly see what I mean.

Replace it with a pair of those BIG yellow slide terminals, not the little ones that look like normal ones, but the BIG ones.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Thanks guys! It turned out to be the relay on this one.