I've joined the club... I never really had a boneheaded moment when fixing cars, except when a 993 tried to crush me but now I have in a big way... My car came back from 1+ year of resto with 2 new batteries fitted by the mechanics. I noticed they fit poorly and one was dangerously close to contacting the battery box with the + terminal. Like 2mm close, one bump and boom...
So I did the right thing and ordered 2 correct ones from Lauderdale Electric, sonnencheim or something... Also replaced the aging connectors... That's where I screwed up. I did not question the cable colors... they were red, I bought red, and red = + in my head. The new batteries fit so much better and I saw the terminals were reversed vs. the old batteries I had but that is where I brain farted: I did not realize that on my car, ground cables were red and positive were black, which is reversed from normal (my normal anyway). I went red +, black neg- not questioning that the posts were reversed now and the cables should have been too, and.... sparks galore.... the ground connector got hot, I immediately went WTF and disconnected everything within 5 seconds.. I then engaged my brain and noticed that red was direct to the body so it was the ground... $%#$%$#%$... beginners mistake.
I am pretty sure I fried my alternator. The car starts, runs well on 2 fresh batteries, but voltage remains the same with engine running, not alternator output, and the alternator light is ON when the car is not running. Oh well, if it were an FAA accident report it would read: Crappy battery installation by the mechanics caused the owner to replace batteries needlessly, and wrong cable color did not cause warning signs in the befuddled owner's brain. Owner is a dumba$$ with some mitigating circumstances... ;-)
Apparently I can get the alt. rebuilt for less than $100, probably a diode. Any chance I did more damage in 5-10 seconds ? the car runs fine except for the alt... If I decide not to pull it myself, can I drive 5 miles in the city on the 2 batteries only ?