vida

whats up, i just got a 1987 mustang recently and seem to be having a batter draining/charging problem, i replaced the battery earlier today and got the alternator check and it was puting out 15.83v so i have no idea what could be wrong, it runs fine and so far would start fine durring the day but tonight i was leaving work and had to jump it off, then was driving home and about 2 minutes after i left the lights were pretty much out because the battery was dead, and i would think the power from the alternator would be plenty to power headlights and all. the power comming from the alternator was checked at the battery posts so how could it not be chargin it?? when the car is at high rpm the volt meter goes up to 12 or 13 but when sitting at idle it slowly goes down, has anyone had the same problem?? thanks

Liquid_02

If i read that correctly... your alternator is charging at 15.83v... time for a new regulator.. or alternator if you don't want to deal with that.

vida

you were right! i went back and took the alternator out and tested it and it failed all 3 tests, dropped a new 1 and its workin like a charm, thanks!

mu$tang95

I have the same problem on my 95 5.0 I replaced the alternator it pumps out 14.6 volts, replaced the battery, and terminal cables, even with a brand new alternator the battery still drains.

When I first start the car the battery is properly functioning plenty of amps, but then after 30 min of driving, the amps at idle will rise and fall with my RPMs Something is pulling power away from my battery while driving, I thought it was my cables because they looked a little sketchy, but that did not do the trick any help is much appreciated!