I have a 2007 Ford focus after about 30
seconds of engine running my battery light
comes on .I have changed the alternator the
serpentine belt and the batt.
Sounds as if you have a bad ground, check all the grounds on the car, I think there is a total of four on your car, clean with a wire brush
This vehicles charging system is computer controlled, so if there is a glitch in the programming it could be shutting off the alternator, a good scanner will have a live data test mode then you can actually see what the computer is doing.
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