Testing Alternator Amperage
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Testing Alternator Amperage
Can you test an alternator's amperage output with a multi-meter, or do you need special test equipment that puts a load on the alternator?
I can't get any amp readings, but the voltage is good.
Scott
I can't get any amp readings, but the voltage is good.
Scott
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From: Virginia
Testing Alternator Amperage
The multi-meter is the only way I know to see if it's output is satisfactory. Of course to run it through it's paces, you would have to put a full 12 volts on the field, turn it a certain rpm, and let it dump into a load of some kind, like you suggested. But I don't know of anybody who has such a rig to test them like that.
To put it through a load test at home, turn everything on in the truck, headlights, fan blower, etc., and see if the voltage stays at least 12 volts at the battery. If it goes below 12 volts with the rpm up, it's not keeping up. Don't panic if it can't keep up at low rpm.
To put it through a load test at home, turn everything on in the truck, headlights, fan blower, etc., and see if the voltage stays at least 12 volts at the battery. If it goes below 12 volts with the rpm up, it's not keeping up. Don't panic if it can't keep up at low rpm.
Last edited by Franklin2; Jul 26, 2003 at 04:36 PM.
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From: Durham, NC
Testing Alternator Amperage
I agree, monitor the battery voltage while turning all the accessories on. It should be able to maintain at least 12.6V,
at elevated RPMs. When you do this make sure the battery
is fully charged. A discharged battery will take a lot of current
from the alternator...
at elevated RPMs. When you do this make sure the battery
is fully charged. A discharged battery will take a lot of current
from the alternator...
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From: Southern California
Testing Alternator Amperage
Thanks guys!I'm look'in at replacing the battery, but I just wanted to try and eliminate the alternator as the source of the problem. When I tested the alternator output with the volt-meter, I got over 14v. I'll give it another go with lights, fan and as many accessories as I can run. But so far with the comment's you've made about voltage output, the alternator is probably okay.
Scott
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From: Central Kali
Testing Alternator Amperage
I made a load bank using a bunch of headlamps. Each one has it's own switch so I can set the amp draw on the alternator. Got the lamps at a wrecking yard for a buck or two. I now have a lifetime supply of headlamps. 
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