So while driving my 99 mustang lately, once up to operating temperature my battery light comes on for about 10-20 seconds, and then goes back off on its own. Has done this during acceleration and during cruise, also today it came on twice, going off both times in 10-20 seconds. Both the battery and alternator have checked out good in testing done by checkers. No changes have been made in the electrical system. My mechanic and I are both stumped. Are you?
My guess, possible bad diode in the alternator, the voltage regulator is getting ready to go, or a bad connection somewhere. Most bench tests only check to make sure the output is within normal limits (12-16v), but if it's allowing the voltage to go above or below the normal limits, it will trigger the light.
Where is the voltage regulator located? That was my next guess but don't know where its located or how to go about testing it.
Mine does this as well. It has done so ever since i installed a tune via handheld. Car has perfectly fine voltage, light just comes and goes.
I had the same problem. I replaced my battery terminal connections because they were all croded and that fixed the problem.
