Don't like the adverts?  Click here to remove them

Alternator bench test

Mick W

Well-Known Member
Joined
Mar 2, 2020
Messages
434
Country Flag
great_britain
Anyone have any details for resistance readings to bench test a 90 series alternator? No output while on the vehicle so I'm wondering if it's simply a failed resistor or new unit required. TIA
 
AFAIK the only discreet components inside are diodes, coils, and the regulator. I had mine apart recently and didn't see a resistor inside.

Should be testable on the bench though by connecting I, S, and the main stud to a 12v battery, negative to the case, then spinning the alternator to 2000rpm and checking for about 14.4v on the battery.

How many miles has your 90 done? Just did brushes on mine in its second alternator. Car has done 382,600km
 
Last edited:
AFAIK the only discreet components inside are diodes, coils, and the regulator. I had mine apart recently and didn't see a resistor inside.

Should be testable on the bench though by connecting I, S, and the main stud to a 12v battery, negative to the case, then spinning the alternator to 2000rpm and checking for about 14.4v on the battery.

How many miles has your 90 done? Just did brushes on mine in its second alternator. Car has done 382,600km
Thanks AW. Mine has 225k miles and it looks like it may be original unit. I’ll try the tests you’ve suggested and report back. Felt good to be out under the hood today with all this crap weather we’ve had. Cheers
 
Thanks AW. Mine has 225k miles and it looks like it may be original unit. I’ll try the tests you’ve suggested and report back. Felt good to be out under the hood today with all this crap weather we’ve had. Cheers
Might be worth just trying the brushes first if you can't see any other sign of problems. My brushes were about A$35 from Toyota so worth the risk versus a replacement alternator, especially when you consider the only affordable ones are the remanufactured B grade brands. However the diodes and regulator are also available IIRC.

Also depends how much time you have without the car of course. Good luck mate.
 
Back
Top