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I have a 2003 Silverado and the Volt gauge will drop from 12 to 9 just randomly. When it drops the ABS and Brake light will come on and chime. I had the battery and alternator tested already. If I turn the blower motor up it will dip down and bounce around. The same goes when the power windows are used. The headlights do not really dim much, but the dash lights will dim and the blower motor will slow down. The truck has never died because of the low voltage. I have checked the grounds and the connections. What else should I look for?
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Sounds like an alternator to me. You shoule be around 14V or better not 12. Ive seen many a regulators fail intermittently. I would get a DVOM on the battery and also check the inputs to the alternator when it is failing. If the inputs are good the alternator is toast. -
Agree sounds like the alternator is going out when under a heavy loadComment
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The gauges in the Gm trucks are known common failure points. I agree with the above statement about using a Volt meter and checking voltage at the battery. The volt drop with the blower speed increase, power windows, power seats, using turn signals, etc is somewhat normal. The alternator doesn't just instantly account for large amp loads like these. You will see a dip in voltage and if the load is sustained the then alternator should bring it back up accordingly until the load is turned back off.
I also agree that it sounds like an alternator that is failing. I do recommend making sure the battery connections are good and tight. If you can wiggle the cable at the battery ANY at all it is loose. The battery bolts are generally softer material than the battery threads themselves. If it strips or feels like it won't tighten enough buy a new set of bolts, they are cheap.Comment
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I have an 02 that did the same for 4 days before the alt. finally gave up the ghost.Comment
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