Measuring alternator output (Amps)?

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Nov 30, 2004 | 02:00 PM

Neo

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Measuring alternator output (Amps)?

What is the best way to measure the alternator output? I assume it would be an ammeter that can measure in the amps in the hundreds. I picked up a high output alternator (not JPI) but wanted to verify the output level. I also wanted to check the OEM output. The two Norcal shops I know don't have a way to measure this.

Nov 30, 2004 | 02:16 PM

RTIS250

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You need to get a load tester... not somethin you can or would want to just pick up at the store. An inductive pickup on an ammeter probably wont be able to measure the amount you're looking for, simply because you have to load the alternator to measure output, and the ammeter cant load the system, it can only measure. Where are you in CA? Im suprised to hear that your local shops dont have a battery/alternator load tester

Nov 30, 2004 | 04:47 PM

Neo

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You mean the unit would put the load on the alternator and measure? What about if the alternator is installed? Can a simple ammeter measure it then and have the car put the load on it?

I was surpised too about the shops too. Looks by your sig, you are in NorCal. So am I. Do you know a place that has the equipment to test it?

Last edited by Neo; Nov 30, 2004 at 04:47 PM.

Nov 30, 2004 | 05:32 PM

HarrierAWD

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Just go to AutoZone, they test alternator and battery for free.

Nov 30, 2004 | 06:29 PM

RTIS250

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Quote:

Originally posted by Neo
You mean the unit would put the load on the alternator and measure? What about if the alternator is installed? Can a simple ammeter measure it then and have the car put the load on it?

I was surpised too about the shops too. Looks by your sig, you are in NorCal. So am I. Do you know a place that has the equipment to test it?

The machine we use tests the alternator while it is installed in the car. Just hook up clamps to the battery terminals, and an inductive clamp on either the positive bundle or negative bundle of wires coming off that terminal. The machine pulls a load on the system, and the inductive clamp measures output. I suppose it could be possible to measure load using the car as the load, but it wont be consistant, and you wont get a full measure of the output. And i dont beleive an off the shelf ammeter will be able to measure over 100 amps safely.... it would need to be a high quality inductive ammeter.

I know of a few shops in Fremont that have the capability to test your alternator while its in the car. I beleive, like said above, an autozone location can test it outside of the car.