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Discussion Starter · #1 ·
How can I tell if my alternator is working? The Battery in my 67 went dead a week ago. I Checked voltage at the battery after jumping it to get it started and was at about 10 volts. Ran a jumper at the regualtor and the alternator kicked on. Replaced the regulator and am getting 14.5 volts when the car is running and about 12.5 with it off. Can I assume it's working properly just by checking the volts or should I have it tested under a load for amps?
 

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Discussion Starter · #2 ·
The engine seems to turn over slowly and then fires up and runs fine. Can I pull the negative battery cable and see if she still runs to check the alternator?
 

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if you get 14.5 volts running and 12.5 not running, I think your alternator is fine.
 

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DO NOT pull the cable off the battery to "see how big the spark is". That can destroy an alternator.

Your voltage is good, but don't assume the amperage is ok. You need, at minimum, to load the battery by cranking the engine, turning on the headlights, wipers, radio, dome light, etc. Then start the engine, connect an ammeter to the alternator output and measure it at fast idle. Better be close to the amperage rating stamped into the alternator case.

A better way to do this is to pay a shop to perform a cranking/charging test using a variable resistor (carbon pile) to load the system.
 
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