Battery light comes on .

Asked by Jan 03, 2016 at 05:29 PM about the 2003 Ford Mustang Premium Convertible

Question type: Maintenance & Repair

2003 Mustang V6. Changed rebuilt alternator and new battery. battery light comes on after about 5 minutes engine is running. Had alternator checked and battery. Both are fine. (O Riley parts) Disconnected positive lead for 20 minutes to clear computer code. Reconnected and started engine. Still battery light comes on. Ground wire has good ground. What can be the problem????? I am stumped as well as the O Riley people.....

3 Answers


What was the alternator voltage reading ? Also check for blown alternator fuse or relay.


Ford was introducing pcm controlled charging at about that time and sometimes the replacement generators weren't wired for it. If it generates a cannot control voltage code it's the wrong generator or a pcm issue.

1 of 1 people found this helpful.

As mentioned already, verify the voltage at the battery terminals when the car is running (should be upwards of 13.5 volts to 14) Also, check for loose connections of the back of the alternator. For your 2003 3.8 mustang, you should have two: one grey connector that clips vertically to the back of the alternator, and one metal loop connector that is held in place by a nut. CAUTION: disconnect the battery when checking the connection that is held in by the nut, as you could shock yourself.

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