Is my alternator working properly?

I’ve been working on my car for a few days because alternator was not charging my battery at all. I replaced alternator, belt and battery, tightened belt, cleaned connections and now it shows 14.38 volts with engine running / idling, which is good, but now shows 13.13 volts with engine off. Do you think my alternator is overcharging? Not sure if I should loosen the belt a little, it goes about 1/2 inch down when I push it hard from the middle. I’m scared that my battery will explode because it shows 13 volts when engine not running which is above full charge. I put blood sweat and tears into this over the past week...


UPDATE: It appears to be a surface charge. I went to check it an hour later and it was at a normal 12.8 volts. :-)

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1 Answer

  • Anonymous
    1 month ago
    Favourite answer

    That is normal battery voltage immediately after shutdown.  Battery engineers call the excess voltage "surface charge". You have to wait for about 4 to 5 hours or maybe even overnight and get the reading again to see the correct charge.

    If you do not want to wait, with engine off, turn the headlights on for a minute to a minute and a half to remove the surface charge and read the voltage again.  Voltage should be just above 12.6V or maybe a tad lower.  Good luck.

    • Dillon1 month agoReport

      Thank you :-)

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