Screwed Up Installing Alternator; Please Help


New Member
Mar 30, 2017
Hi, I'm fairly new to this forum. My battery and alternator recently failed on me so I decided to take it upon myself to purchase and install a new set. It was a fairly easy job and I was done in under 20 minutes. Now, when I bought the new alternator it's pulley had a diameter that was about 1/3 of an inch smaller than the previous one in my car. I didn't put too much thought into it due to the fact that the sales guy assured me it was the factory size. I took it out for a spin to make sure everything was good, and right off the bat I noticed the battery gauge drastically dropping. I thought maybe the alternator just needed a second to get going, so I kept driving. That's when my problems started. I could feel the car starting to die before it started shaking and sputtering pretty bad. I was close enough to home that I wanted to try and make it to my driveway. The car completely died a few times while driving, so I engaged the clutch and threw it in 2nd gear and popped the clutch. I had a lot going on while finishing up the alternator job and stupidly forgot to reconnect the two cables to the alternator. It looked as though the belt was what was smoking, although I'm not entirely sure. Can running the alternator with the belt attached, neither of the two cables though, ruin the new alternator? Can anyone explain what happened? Thanks so much in advance!

Oh and my car is a 2000 Mustang GT.
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Mustang Master
Nov 6, 2016
No expert but I would put an new belt on after reconnecting the harness and try it. With a new belt and properly working tensioner you should be OK.


10 Year Member
Jun 2, 2005
Joplin, Missouri
Take it off and have it tested. I never get a working parts store alt the first time it seems. Odds are you didn't hurt anything as long as it's a good unit.

Also good advice on replacing the belt if you've not recently. Broken belt means no power steering or brakes and that's a lot of fun.