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Old 10-09-2010, 01:07 PM
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Voltmeter reads low, charge light off

I'm inclined to believe the light would illuminate if there was a real charging problem. VM reads 10-12 instead of usual 12-14. Occasionally goes into normal range, then drops out again.

Common Delco 3-wire s-12 or something like that. Car seems to be ok, starts fine, just don't want to get caught with a dead battery after dark. VM does drop a little bit with load such as lights or fan, but I still think I should trust the light. What would cause the VM to read flaky?

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Old 10-09-2010, 01:27 PM
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I would check the voltage at the battery to see how accurate your dash VM is.

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What would cause the VM to read flaky?
Bad gauge or bad ground.
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Old 10-09-2010, 02:03 PM
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If this low voltage issue has just started it is probably the alternator going bad.
But make sure the bulb is good.
Key on with motor not running - bulb should be lit.
Some cars the bulb test is only during start or shortly after start.

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Old 10-09-2010, 02:54 PM
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Sounds like your brushes may be going or you have a bad ground. Either of those could cause it to come and go. As someone else state check at the battery and the power stud on the alternator to be sure it isnt just a defective gauge.
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Old 10-09-2010, 03:20 PM
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I don't believe it's a ground because the car has redundant grounds everywhere. Gauges share a stud grounded direct to battery with 8ga wire. Alternator is double-grounded to engine mount as well as adjustment bracket. Engine mounts grounded to frame with 2ga battery cable.

Alternator is only a few mos old and was a quality Delco reman. Lights are bright and starter does not drag. I'm thinking gauge or gauge wiring. Other gauges are ok.
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Old 10-09-2010, 04:56 PM
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Put a meter on it and compare voltages
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Old 10-11-2010, 03:30 PM
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Follow up: Bad connector at starter end of alternator wire. Appeared intact, but had vibrated loose down to a few strands. Thus easy start and run, but poor charge.

I broke the #1 rule of troubleshooting: check easy things first!
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