Voltage fluctuating
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Joined: Sep 2017
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From: Kalkaska MI
Voltage fluctuating
I have an 88 convert. with a recently killed battery. Battery is only 2 years old but will not take a charge. I work from home so this car does not get driven as much as I would like. I can start it with a jump from 2nd vehicle, and after disconnecting the jumpers the car runs but the voltage gage on the dash will vary from 14.2 to 14.5, up and down. After the car is shut off, it won't start, battery still dead. Question, is this a bad Alternator, voltage regulator? Thanks, in advance
Melting Slicks
Joined: Jan 2014
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From: Lunenburg MA
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Joined: Sep 2017
Posts: 72
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From: Kalkaska MI
DO NOT DO THIS, the alternator does not output clean power by itself. It needs the battery. You can toast your electronics. Have the battery tested, it's probably bad. They often don't recover if left discharged for a long period of time. Use a battery maintainer on your new one.
I know the battery is shot. But I wasn't expecting to see the volt gage fluctuate like that. I would have thought the gage would start high (14.5 ish) and continue to drop as the alternator tries to charge the battery.
So you're saying, a bad battery can influence how the alternator works?
Instructor
Joined: Sep 2022
Posts: 209
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From: Dalbo, Minnesota
Is the fluctuation coinciding with the a/c compressor cycling?
weak battery or poor connections will give a voltage dip when an electrical load is turned on or off.
fully charge the battery with a charger. Don’t expect the alternator to charge it at idle or short trips.
If you have an old school charger with a transformer go ahead and charge. If you have a new electronic charger disconnect the battery from the car before charging. Old vehicle electronics don’t like the voltage spikes from electronic chargers.
weak battery or poor connections will give a voltage dip when an electrical load is turned on or off.
fully charge the battery with a charger. Don’t expect the alternator to charge it at idle or short trips.
If you have an old school charger with a transformer go ahead and charge. If you have a new electronic charger disconnect the battery from the car before charging. Old vehicle electronics don’t like the voltage spikes from electronic chargers.
