ady 1 Posted December 28, 2010 Share Posted December 28, 2010 hi to all how do you test a battery/alternator with a multimeter.just want to check my alternator is charging as it should be.any help greatly appreciated Quote Link to comment Share on other sites More sharing options...
suggs Posted December 28, 2010 Share Posted December 28, 2010 Put the tester on the battery terminals with engine running, should get around 14.5 volts... Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted December 28, 2010 Share Posted December 28, 2010 Sometimes more than tickover to get 14.5v! Any higher, it will boil the battery, much lower it's not charging. Turn the headlights on, maybe the heater fan as well, the voltage may drop, but it shouldn't be by too much. Cheers Peter Quote Link to comment Share on other sites More sharing options...
robhybrid Posted December 29, 2010 Share Posted December 29, 2010 engine not running battery voltage as low as 9v (much lower engine may not start). as cranking engine voltage would drop by how much depends on the size of your battery and power of your starter motor. with engine running initially voltage will return to pre starting voltage then rise to between 13.8-14.2 volts alternator has died or there is a strange external load on battery if you do not see the voltage rise. check quality of earth on engine and alternator, quality of live to alternator. with one terminal of multimeter on alternator casing and other on battery neg the volt meter should read 0v. with one terminal of multimeter on alternator live and other on battery poss the volt meter should read 0v. if the readings are above 0 then there is a fault with that line. with engine not running and ing on the ign light should be on in cab and should go off when the engine is running. If the ign light is not on with ign on then take ign wire off back of the alt and touch it against a good neg source the light should come on if not check bulb first then wiring. Quote Link to comment Share on other sites More sharing options...
DrRob Posted December 29, 2010 Share Posted December 29, 2010 with one terminal of multimeter on alternator casing and other on battery neg the volt meter should read 0v. with one terminal of multimeter on alternator live and other on battery poss the volt meter should read 0v. if the readings are above 0 then there is a fault with that line. Is this with engine running? Ta. Quote Link to comment Share on other sites More sharing options...
robhybrid Posted December 30, 2010 Share Posted December 30, 2010 yes sorry with engine running Quote Link to comment Share on other sites More sharing options...
ady 1 Posted December 31, 2010 Author Share Posted December 31, 2010 hi to all just tested battery/alternator with multimeter getting a reading of 14.27 across the battery terminals.is this good or is it to high.also tested alternator direct with multimeter getting a reading of about 14.27 and 14.30 is this good or is it to high.these readings are with engine running at tick over when engine is warm Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted December 31, 2010 Share Posted December 31, 2010 Those readings are fine. 13.8 - 14.5 is the usual range Cheers Peter Happy New Year! Quote Link to comment Share on other sites More sharing options...
ady 1 Posted December 31, 2010 Author Share Posted December 31, 2010 Those readings are fine. 13.8 - 14.5 is the usual range Cheers Peter Happy New Year! thanks for the quick reply happy new year to you as well Quote Link to comment Share on other sites More sharing options...
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