Look for the black wires that go to back of defrost knob for damage. Also on the lighter circuit from the blower motor 6 pin connector female side. As I said in my email there are a number of parallel circuits feeding devices on that same circuit.

At a minimum, as others have said you need to run the overloaded wires down, replace it/them and make sure that the overloaded wire didn't just burn its own insulation, but did not melt adjoining wires. I would also find and pull this fuse until you check it all. Sounds like you were running the compressor off the cig lighter, and I believe it grounds directly to the chassis, otherwise you would have to check ground wires as well. Once you locate the problem wire, replace it. I would also check the fuse in that circuit. It should have blown. With these old cars, you never know what a PO did, so it is possible it is wired directly to the battery unfused much like the black/red wire that runs through the gauges (at least in my 76) Most of all, take your time, dont cut corners.

You definitely need to unwind or cut off the harness sleeve to inspect for damage. Here's a wire sleeve that I thought looked a little crinkled ... After I sliced it open with a razor, to check, I found the black wires and completely burned off its insulation.
http://forums.pelicanparts.com/uploa...1452383241.jpg

But that heat also took out the two other wires running alongside in that sub harness. You need to follow them back into the harness until you get to good, unmelted wire and slice in new from there.
http://forums.pelicanparts.com/uploa...1452383433.jpg

Timmy2 will set you straight after you've identified the extent of damage and removed it from the car. Which depending on what it is and where it is, can be a formidable task...

As an aside to your bigger wiring issue, your post reminded me that I tried using the OE air compressor one time prior to shelving it in favor of a $28 unit from Slime / Amazon...

http://forums.pelicanparts.com/porsche-911-technical-forum/898052-i-shelved-my-28-year-old-oe-air-compressor-got-slimed.html#post8951335

Good luck with your harness work. That shyt keeps me up at night. I've got the front condenser and evaporator blowers fused. I still need to take the five minutes to install a mini ATC fuse (I need to source one first) in-line for the instrument lighting wiring harness. They may not have bothered with cup holders, but ashtray lighting? Awesome '80s!

https://amoroso.smugmug.com/photos/i...-wfmkCnX-L.jpg