Alternator Amp test

[Mattax]

Here's the results from a chain store tester

What's it tell us?
Exactly.
Not much.
The machine must have put a load on it, but what that load was and how fast it was spinning is unknown.

Here's the test results from the rebuilder factory. Same alternator.
It's quite a bit more informative.

What's the amp rating ?

 

[toolmanmike]

Here's the results from a chain store tester
View attachment 1715750400 View attachment 1715750401

What's it tell us?
Exactly.
Not much.
The machine must have put a load on it, but what that load was and how fast it was spinning is unknown.

Here's the test results from the rebuilder factory. Same alternator.
It's quite a bit more informative.
View attachment 1715750402

What's the amp rating ?

I don't see any amperage specs on the parts store sheet. I can damn near do that with a voltmeter under the hood.

 

[Mattax]

I don't see any amperage specs on the parts store sheet. I can damn near do that with a voltmeter under the hood.

My guess is that Battery volts is a load test simulating a battery being recharged by using a known resistance. Its probably a moderate load with the alternator being spun fairly fast, but I couldn't guess what the speed was. Since the accepatable range is in Volts rather than amps, I agree its a really crude test. There may be some inputs the store employee sets to adjust the load or rpm for different units. Need to find someone who spent some time running such testers (and paid attention). My recollection was the only thing they did was look upo (or ask someone who knew) how to hook up the test leads. Probably different setup for self exciting and internally regulated alternators.

The test report from the rebuilder is pretty useful.
There still are some curiosities.
For example, why is the Voltage Set point14.6 Volts but the output test 13.2 Volts?
That's becomes even more of a head scratcher when I reveal what type of alternator this is.

Now that people have had a chance to decide what they think the alternator rating is, I'll post the top of the slip.

If you figured it out correctly, let me know how you did it.
(Its a GM 12SI)


I've posted the next one before.
Looks like the same rebuilder factory.
Came with a revised squareback alternator.

Again, where does the rating come from?
Is the rating this based on the same criteria as Chrysler or any other company uses?
Maybe, maybe not.

One thing for sure. If any of us discovered the altetrnaor was only producing power at 13.2 Volts, especially above idle speed, we would be looking for a problem.