2004 mustang v6 battery light comes on above 2500 rpm

Asked by Dec 16, 2016 at 04:15 AM about the 2004 Ford Mustang

Question type: Maintenance & Repair

I'm having a problem voltage stays steady
13.2 when shut off and when it's running
it's 14.5 charging normal but when I rev it
from an idle or driving past 2500 rpm the
battery light will come on and the
alternator will charge at about 15.2 idling is
perfect just when it's above 2500 rpm the
battery light comes on the car is a 04 v6

1 Answer


15.2 is a little high, 14.8 is the limit, so either the computer is commanding the regulator to get more power or the regulator is stuck in full field mode, this needs to be checked out by someone that knows about computer controlled charging systems, and do it quickly as high voltage can damage all the electronics as well as the lights and battery, and that an get expensive really fast.

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