Can I test my alternator by measuring the voltage on the battery terminals when the ebgine is running?
What sort of voltage should I measure if the alternator is ok?
Thanks Alex
If it helps know more about the car then it's an old car (Mazda 1.3) from about 15 years ago.
yes you can you *should* expect around 13-14 volts .
Yes.
About 13.8 - 14.4 volts.
Corr! Is that all? When I take the battery out and charge it with my cronky old 4 amp charger I get a voltage reading of 15.2 volts while the charger is attached.
Then you've either got a very sick battery with a high internal resistance or an even worse voltmeter...
You are talking about a mains charger but your original question is with regard to your cars ability to charge the battery. If your readings are around the 14v mark then I'd be happy and not mention the cronky old charger.
Dave
That cronky old charger is unregulated, if left for longer than the time required for a full charge it will damage the battery. The alternator voltage is regulated and keeps the battery at a voltage that it will charge up at but not suffer reduced life. Any more than
14.5 volts will start causing other problems like burnt out bulbs.With all the lights on the voltage should rise from about 12.5/13v at idle to 14v at 2000rpm. Any more than 15.5v is usually a faulty regulator in the alternator and it needs fixing.
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