01 Mustang GT battery light won't go off

Asked by Feb 26, 2016 at 09:54 AM about the 2001 Ford Mustang GT

Question type: Maintenance & Repair

Battery light will not go off. Alternator shows charging  13-14 volts running, battery shows 13 volts with motor off. When I unplug the connector in photo, the battery light goes off but alternator drops to 12v and so does the battery. Plugging the connector back in turns on the battery light and there is an audible change in the sound of the alternator. according to the schematic, the connector has a light green/red wire that goes to the battery light and a yellow/white stripe wire that goes to the under hood fuse box. Is this a wiring issue or is there something going south with the alternator/regulator?

4 Answers

Tom Demyan

Alternator should show 13.8V -14.2V if working correctly and battery should be around 12.5V. Not sure what you have going on, maybe someone else will chime in. Maybe remove the alt and have your local auto parts store test it?


A battery light indicates your system is discharging. First place to look would be the alternator so, I agree with "Tom" - have the alternator checked out before anything else. I believe the connector you are pulling out controls the "Battery" lamp on your dash so I would expect the light to go out when you pull the plug. One other thing, are you sure your belt is tensioned properly and it is not slipping?

1 out of 1 people think this is helpful.

The belt is tight and no signs (or sounds) of slipping. It seems to be charging OK even with the connector for the battery light and the wire that goes to the fuse block unplugged. Wife drove it to work and back and I checked the battery, showed about 12.5 volts. Doesn't seem like there's any charging issues...just a battery light that won't go off unless it's unplugged. I have never had an alternator that "kind of" worked out. . I thought they were more like "it works fine or not at all".


I have / had similar issue. I had bought a used 2000 GT, it was in a bad state. The alternator had only 2 wires and the light was on. In all the places I have checked it should have 3 wires running into it. Yellow, White and Green.

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