I have an 86 f150. The other day I was driving along here in sunny (read hot and humid) Florida and the AC stopped blowing. I figured it had something to do with the blower motor resistor so I changed it. My truck laughed at me and said no. I checked the fuse and it was blown so I replaced it. Then the blower worked great. As soon as I switched it to AC though, it blew the fuse again.

Is this a compressor issue or something different?

 

Your compressor clutch could be shorted. I've seen it happen before.

Back to the fan motor, is it the original?

Know how to use a volt/ohm meter?

 

I'm pretty sure it's the original blower motor. It does run if I replace the fuse and leave the selector on vent but if I pass the switch over the AC controls the fuse pops.

I do have a V/O meter and know how to use it. Would I be testing for continuity or something more specific?

 

My first thought is to pull out the radio and look behind the HVAC controls, see if mechanically moving the levers has worn away the insulation on some wiring that might be interfering with those controls.

 

With your meter, look for continuity between the coil connections and the case of the compressor. OR pull the plug there, install a new fuse, and see if it blows again.

The coil on the compressor clutch can, and does, short out.

 

Great suggestion, thanks. My mind always assumes the worst, and therefore the most expensive, when something simple is usually the answer. However, everything appears to be in good condition back there.

 

Thanks for all your help everyone.
I was all set to do this and then I found my problem. This was a classic case of AC compressor wiring meets alternator pulley.

Somehow the wiring got wrapped up in the pulley and the fuse did exactly what its supposed to and kept the truck from catching on fire.

 

On my truck, the wires to the clutch run along the suction hose line over to the compressor from the firewall area.

Glad you found it. Glad the fuse blew for you.