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Battery Gauge Randomly Fluctuates Towards High

I recently had problems with my alternator not charging my New Battery. I ended up replacing it with another one. I made sure the new alternator was the proper one for this vehicle. This make includes an internal regulator within the alternator, just like the old one did. The new alternator was working fine up until a few weeks ago. Recently my battery gauge has randomly been fluctuating towards the H “high position”. The fluctuation happens when parked and driving while increasing engine RPM’s. Any ideas of what could be causing this?

First check all the wiring connections to the alternator just to be sure they are all tight. Same for the battery cables. If that’s OK, it could be a bad gauge or it could be a faulty voltage regulator in the new alternator.

Attach a real voltmeter to the battery temporarily with some wires long enough to allow you to mount the voltmeter where you can see it (tape it to the windshield) and drive it exactly as you describe to make the car’s gauge act funny. Compare your voltmeter readings. If the voltmeter you added is a steady 14.5 volts (or around that point) it is likely a faulty gauge in the car. If the voltage reads too high (over 14.9 volts) or jumps around, it is very likely the voltage regulator in the new alternator. Good Luck and post back on the results.

Well I only buy Delco rebuilds for my GM cars because they use new parts. I do believe that some rebuilds just use many of the old parts like the regulator and clean them up. As long as the bearings are fine and it charges, in the box it goes to the retailer. So unless it was a brand new one, I’d suspect a faulty regulator. I have had them before fluctuate and dim and brighten the lights but still OK under warranty. Finally just threw it away and went with Delco and never looked back.

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As an alternate, you can buy voltmeters that plug into the cig lighter socket for about $12 at A great diagnostic tool. I have one that also reads cabin temperature.