1989 Ford Mustang Battery Won't Stay Charged

FULFAM

MEMBER
1989 FORD MUSTANG

Engine Mechanical problem
1989 Ford Mustang 4 cyl Automatic A Lot! Miles

The other day, my husband drove the car to work like always and it wouldn't start when he tried to come home for lunch. He said the battery was dead and replaced it. He drove home that evening with no problems, but the car had to be jump started for him to drive to work. He said it was because he didn't tighten the battery terminals enough, causing it to lose its charge overnight. He replaced the battery terminals with new ones, but the battery still won't hold a charge. Finally, he took it to Checkers to have the battery and alternator tested, but they tested okay (please note the girl who did it didn't know how to read the machine). We've made sure EVERYTHING is turned off during charging, but it won't stay chraged. What else could the problem be?

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

Get an analog voltmeter remove the negative battery cable, attach the Black lead to the battery post, Red lead to cable end, then pull fuses one at a time, make sure there are no accessories or lights in the on position, Key off! Close the door after each fuse and check meter, when you pull the fuse for the bad curcuit, the meter will drop to 1 volt or so. Check all fuses, even under the hood. If meter does not drop, remove the battery connection from the alternator, if it drops now, the diodes are bad in the alternator. Put the fuse back in were it goes as you go so you don't forget which fuse goes were!