Here's how all this started:

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/can-re-grounding-lead-death-alternator-91-auto-manual-coupe-610516/

When I took it in, they replaced the alternator and the rebuilt one immediately died. The only way they could even the electrical pull was by unplugging my a/c, but at the time it was January and I was just looking to get the car out here asap.

Well, three days of hard driving and the car was doing fine, except when it was really cold (below freezing and snowing), I could hear the belt start slipping - this was happening whether the car had been driving for a while or had just been started, and it happened when I was switching low gears (mainly, into 2nd). If I was really conservative about switching the gears, the belt wouldn't slip. I assumed that the mechanic had for some reason left the alternator belt too loose and did what I could to make it back to LA, and aside from the noise it got here fine. When I got to LA (which was considerably warmer), the belt tension seemed to be fine, I didn't notice any other warning signs, and I couldn't get the belt to slip on command, so I chalked it up to bad weather and tried not to drive too much on it until I could get it looked at by my mechanic.

Well, a week into driving around here, the same slipping noise started happening, and then suddenly while I was on a local street, all the dashboard lights went on as if I had an alternator problem, and the battery gauge read that the battery was slowly being overcharged every time I touched the gas pedal, and also every time I had the gas going for more than 1k rpm the noise started up again. As soon as I stopped giving it gas the noise would stop, the dash lights would turn off, and the battery gauge would slowly go back to normal. I limped home with the hazards on, squealing all the way, and parked it in the school lot until I could take a look at it. (Full time college + no money + live in dorms = can't look at it until May)

Well, now it's May, and I'd been starting it up once a month to see if anything had changed - same noise, same problem with the battery being overcharged - and now, predictably, the battery's dead so I'll have to jump it just to see if anything's changed and if it will let me drive it very slowly to my 7 mechanic.

Since I'm pretty sure all this goes back to the shitty mickey-mouse wiring job my mechanic friend did when we did the auto to manual tranny swap, and since I never had problems with the wiring or alternator while the heater and a/c were unplugged, I think the best bet to get the car to the mechanic would be to disable the heater - but I can't find my fuse diagram and for some reason can't find it online - come on, people, I know it's around here somewhere.

Any other bright ideas on what the problem could be?

EDIT: Seems that my voltage regulator might be shot. Could faulty wiring cause this? If the voltage regulator was shot from the beginning, I'd rather send the alternator back to the mechanic and have them send me one that doesn't suck - but if the wiring's still messing up my alternator, I'd like to know.

 

Sounds like the voltage regulator is shot.