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alternator amperage question

2434 Views 28 Replies 10 Participants Last post by  SIXFOOTER
I bought an alternator at a swapmeet for $4.00....I needed the fan & pulley and the rubber boot is nice also...the alternator is not marked with an amp rating, so how do you tell what it is?? NO I am not going to run two alternators.......
.....redvetracr
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Run it on a vat or take it for your free parts house check. Could have possibly been rebuilt with any amperage windings.
The amp rating should be stamped in the housing. It's hard to see sometimes until it's been cleaned.

BTW - I have two alternators on my Tahoe. What's so wrong with that?

inside joke!!
(Edit: Whatever ... durango boy)

BTW ...does your "Tahoe" have a ram on the hood???? :rolleyes:
...redvetracr
BTW ...does your "Tahoe" have a ram on the hood???? :rolleyes:
...redvetracr
:laughing: :nuts:
(Edit: Whatever ... durango boy)
????????????????????????????????????????????????????????????????????
????????????????????????????????????????????????????????????????????
You'll have to ask a mod:laughing:
You'll have to ask a mod:laughing:
Not so sure I want to know.:laughing:
I bought an alternator at a swapmeet for $4.00....
and you call ME a cheap bastard.

short the regulator with a screwdriver and see what the guage says.
and you call ME a cheap bastard.

short the regulator with a screwdriver and see what the guage says.


should I have paid more than the $4 asking price?? If I had said "I bought a $4 alternator for my race car" THEN you could call me cheap....but not just yet..:nuts: .
...redvetracr
and you call ME a cheap bastard.

short the regulator with a screwdriver and see what the guage says.

Is that the gauge that measures how big the spark is when you short it? Or the one on the tester? :rolling:
Is that the gauge that measures how big the spark is when you short it? Or the one on the tester? :rolling:

What tester?. There is no tester. You take a screwdriver and stick it in the slot in the back of the alt. That causes it to bypass the regulator and go into full boost. Read the amp guage on you instrument console.

You want me to make a video dog and pony show so you will fully understand it?
Easy there turtle-- I didn't means to spin you up. Just havin' a bit of fun. Sorry if I offended you.. :spanked:
Easy there turtle-- I didn't means to spin you up. Just havin' a bit of fun. Sorry if I offended you.. :spanked:
its ok. everybody offends me.
So now that we are all hugging and singing "cum by ya" again, whats the answer to the original question? Is there a way to tell by looking at the alternator what it is?
Not really. You may be able to tell from the numbers on the case, but if someone rebuilt it they could have put the 100 amp rotor/stator in it, or just new brushes, regulator, and diodes. If it's on the car and charging, you can short the tab on the regulator like turtlevette suggested and see what the full output is. if it's not on the car, an auto parts store can test it and see what it'll do. And for $4.00 you can't miss anyway. even if it needs new guts, it's still cheap. AND he got the extra parts he needed to boot.

:cheers:
Maybe I am missing something but I am not seeing how that Test would work.An alternator puts out current at a certain voltage, the current being put out is controlled by the load and the applied voltage. Driving the output to Full will only turn the applied voltage up, the current will only go to what the load allows. So, if you use the headlights for a load and are useing a 140 amp alternator and drive the output to full, you are NOT going to run 140 amps into those headlamps. The voltage might go to 15+ volts, but the amps will not go any where near 140
Maybe I am missing something but I am not seeing how that Test would work.An alternator puts out current at a certain voltage, the current being put out is controlled by the load and the applied voltage. Driving the output to Full will only turn the applied voltage up, the current will only go to what the load allows. So, if you use the headlights for a load and are useing a 140 amp alternator and drive the output to full, you are NOT going to run 140 amps into those headlamps. The voltage might go to 15+ volts, but the amps will not go any where near 140
Test it with dead batteries connected. :laughing:

You really need a carbon pile tester like the vat I mentioned earlier for accurate results.
Here is a cheapie
http://www2.northerntool.com/product-1/200323715.htm
:D
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