I recently endured a problem with my car when the battery went dead while driving. It was the alternator that needed replacing. I was told if I had noticed the voltmeter reading incorrectly, I might have been spared the breakdown. How might this have looked on the meter?
While underway, a vehicle’s charging system tries to maintain a system voltage of around 14 to 14.8 volts. When you see this on the instrument panel gauge, it’s safe to assume electricity is being generated at a greater rate than is being consumed, and not in excess. At idle, with many accessory loads active, voltage may temporarily dip to perhaps 13 to 13.5 volts, as the charging system isn’t as effective at low engine speed, but this is OK. A gauge reading below 13 or above 15 indicates a charging system fault. A low reading may lead to a discharged battery; a high reading may cook the battery and certain vehicle components.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at firstname.lastname@example.org; he cannot make personal replies.
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