# Alternator overcharging, replaced, still overcharging



## cwienands (May 20, 2009)

Hey guys,

recently my battery off my Sentra '01 SE died. Just FYI, the battery lamp on the dashboard never came on. The dealer tested the charging system and told me the voltage regulator was broken. I confirmed this with a voltmeter reading of 15.3V across the battery terminals.

Since the quoted price was superhigh (Nissan alternator + dealership labor) I decided to do the job myself. I got a rebuilt alternator from Pepboys (I know I could have, should have done better) and put it in.

Unfortunately, after I put everything back together (new alternator and new battery) and started the car, immediately the battery warning light came on (which it didn't do before the repair). I again measured the voltage across the battery terminals. Again, 15.3 or .4V :-(

The "obvious" answer is, I got what I deserve and got a poorly rebuilt alternator. However, what's the chance of having two alternators with broken voltage regulators? Therefore my question is, is there anything else that could cause the alternator to overcharge the battery? Poor connections? Other failed electronic/electrical components?

Anybody any idea? I really don't want to pull the alternator out again!

Thanks, Christoph


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## IanH (Feb 11, 2003)

Battery warning light means something is not right in the rebuilt alternator. Replace it.
The warning light system monitors the output from the power diodes and compares to a diode trio. So if the ability to produce current is impaired the light come on before complete failure. ( ie you can have 2/3 current or 1/3 current and car run normally till you load the battery then it will go flat while driving)
So imbalance will cause light to come on.
Re: hi voltage, turn on the headlight and let car idle and measure the voltage.
What does the battery measure with the car off?
Check your meter against someone else's....


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