I figured I'd ask around here before I go to a mustang forum. My buddy is having issues with his 1988 Mustang GT. When he's driving it, it's fine, voltage is 14.4 or close and there are no issues, but when he's idling the voltage drops to close to 10 and will sometimes die on him. His car idles around 800 and doesn't fluctuate so it's not that.

We're trying to figure out what it could be.
-So far he's swapped to a new alternator. I'm thinking it could possibly be an issue with this new unit but who knows.
-He has 2 batteries and neither of them solve the issue and both are good batteries.


He doesn't have problems cranking which is the weird thing, but the voltage at idle is well below what it should be. Let me know if you guys have any suggestions.

 

Sounds to me like the alternator just isn't spinning fast enough to keep the voltage up at idle. Does he have any heavier current draws like e-fans or anything else that might run at idle and make the problem worse?

 

That's kinda what I was thinking. It was a remanufactured unit from autozone so it may very well be the issue

 

Yeah my first suggestion would be to get that AutoZone reman POS off there and put a decent OEM or aftermarket alt in it's place and see how that works.

 

Yea I'd say you're right. Hes come a long way on this car so I can't be too harsh on him but well try and get a new alternator put on and see if it does the trick