How to bench test alternator

[fixkick]

Hi,

I have an alternator from a 98 sidekick kicking around here that I can’t remember if it’s good or not and I was going to sell it  to someone. If I put a drill on the pulley nut and spin it, with the ground lead of my tester on the alternator body and the positive lead on the big stud I only show about 0.5 volts. I know some alternators need to be wired up a certain way to show charging. Not sure if this is the same. I looked at your diagram and was wondering if the charge “sense” circuit needed to be recreated.

Thanks!

what a great question, how to test any alternator off car,  all auto-stores (most) have that machine in the store, to test alternators.  
go there and ask? .
one top failure is not alt dead but bearings shot and makes huge noise spun. fast. and does spin way faster than engine.

98 sidekick, G16 or J18?//??? they are not the same.

the only real test is on any motor spinning and a real battery in place.
try to know that the internal regulator inside, must NOT THINK (detect) that there is a MISSING battery , nor shorted, or the ALT reg, shuts it all down, to prevent 2 things.
1: blowing up a battery (acid flying) and not wreck it self. trying.
2: if battery missing it will not want to run, due to huge possible factors of going over 15vdc and blowing up all electronics in the car and  busted bank account there.


now to answer the question. actual
first off the alternator will  be dead 1/2 the time if the dash idio lamp is missing , the lamp is the self excitation current to get the alternator to boot up, and make power.
the fact is , some alts have residual magnatism in the rotor and self excite ok, but is a coin toss that.

off my charging page is this. G16 ONLY !

1. first is  a real battery.
   
2. then the lamp
   
3. then black-white jumped to B+ big stud , or the alternator will be dead.
   
4. must  be spun fast enough to wake up the REG.  (on car 800rpm is engine but alt is way faster 3 times?) IDK ratio. It say over 200 RPM on ALT.( finger raised to wind)
   

most alts wake up at 600 RPM engine actual. alt spins 3 times faster, see that tiny pulley on alt?>yah. (2" over 6" is 3:1) by seaman's eye.



 
here is REG guts, if lamp is missing, R1 is dead, if there is residual mag. Diode Trio wakes up and feeds R1. and magic happens.
the reg must go online of the rotor coil is dead and so be ALT,  what  cool schematic no?   some cloned ALTS  will  act different !(clone =  random 3rd party makers)
the sense wire is never optional.