anton74 Posted December 5, 2011 Report Share Posted December 5, 2011 Guys, My battery died yesterday and I replaced it with a new one. I measured the voltage across the battery terminals, it was 15.4V at idle, with the lights off. Does it mean that the alternator is overcharging the battery? Should I replace/repair the voltage regulator? Thanks, Anton. Quote Link to comment Share on other sites More sharing options...
AL Posted December 5, 2011 Report Share Posted December 5, 2011 I would say yes... 15.4 is definitely overcharging the battery... A new alternator is decently cheap I think Quote Link to comment Share on other sites More sharing options...
Schurkey Posted December 5, 2011 Report Share Posted December 5, 2011 Guys,My battery died yesterday and I replaced it with a new one. I measured the voltage across the battery terminals, it was 15.4V at idle, with the lights off. Does it mean that the alternator is overcharging the battery? Should I replace/repair the voltage regulator? Thanks, Anton. 15.4V is way high. Is your voltmeter accurate? 14.2V would be about right. Is the battery fully-charged? (no-load voltage at 12.6--12.7 volts) The regulator is INSIDE the alternator, makes no sense to replace the regulator without rebuilding the alternator. Any AC voltage at the battery, indicating failed diodes in the alternator? PROPER testing of the starting/charging power team is not difficult, but virtually nobody has the appropriate tools outside of an auto repair shop. The components in the system will cause each other to fail if they're not ALL good; and it's difficult to tell what's usable from what's failed without a COMPLETE test. Quote Link to comment Share on other sites More sharing options...
anton74 Posted December 5, 2011 Author Report Share Posted December 5, 2011 Thank you guys. I don't know whether my multimeter is accurate. The battery is fully charged and new. How can I check the AC voltage at the battery? Quote Link to comment Share on other sites More sharing options...
Schurkey Posted December 5, 2011 Report Share Posted December 5, 2011 Thank you guys.I don't know whether my multimeter is accurate. Test voltage of a few GM vehicles that don't have problems. See if they show around 14.2 volts... The battery is fully charged and new. Did you TEST the battery? NEW does not mean fully-charged. For that matter, NEW does not mean "Not Defective". How can I check the AC voltage at the battery? Turn the dial on your multimeter to "AC Volts". Connect the test leads to + and - at the battery with the engine running. Quote Link to comment Share on other sites More sharing options...
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