Over the years I have saved the Denso (Nippondenso) alternators on my 740s and 940s before the cars went to the crushers. I have several 80A Denso and 100A Denso alternators.
I removed the brush assembly in an 100A alt. yesterday and there was lots of corrosion which ended with broken screw tabs on the regulator where one tab of the brush assy. screw went. So, since the regulator is a voltage regulator, not a current regulator, I'm wondering if the 80A and 100A regulators are interchangeable. Physically, I think they are, but electrically? I have an 80A alt. with very little corrosion (salt state here) so I think the regulator screws should be easy to remove and I was thinking of putting that regulator in the 100A alt? Of course I could just use the 80A alt. but I'd like to keep that car, a 1994 940, as it was built 25 years ago.
It is interesting that the slip rings on the 100A are not in as good of condition as the 80A units I have seen.
Another question? To test the alternators, should it work to put the alt. in a vice and connect a battery + to the armature output (large stud), connect the battery + to a 12V bulb and the other side of the bulb to the field (sense) connection, and the battery - to the alt. case grd. connection. Then, spin up the alt. with a drill? Monitor the alt. voltage with a voltmeter across the battery. I tried this but don't think the drill spun the alt. up fast enough to get a higher voltage?
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Mine:3-940s running, 1-740, 2-940 parts, dtrs:4-940s running

Thanks Amarin and Spook for the replies.
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Mine:3-940s running, 1-740, 2-940 parts, dtrs:4-940s running

Dear jd620,

Hope you're well. Call Barsanco (1-800-421-3374) and explain your situation. Barsanco supplies alternator parts. I think Barsanco #216-043 is the proper regulator for a 100A Nippon-Denso alternator. If so, and if Barsanco has one, I'd rather get a new and provably correct regulator, than risk a serviceable alternator.

As to using a drill to spin an alternator, I'd guess that most "household" drills don't turn fast enough. For each turn of the crank pulley, the alt pulley probably rotates four times. Thus, At 2,500 engine revolutions/minute [rpm] (= about 65 mph / 100 km/hour) the alternator is turning at 10,000 rpm.

Hope this helps.

Yours faithfully,

Spook

If the regulators are of same dimension, size etc it should work. I would test the alt on the car instead of the bench. The alt is meant to be part of the system ie charging system.

For bench testing you would have to provide some voltage to the D exciter terminal maybe from a spare car battery. Otherwise the alt have to be spun real fast by the drill to get some output (maybe around 3000rpm) using the residual magnetism in the alt's armature. Could use a simple bulb to test output from B+ and alt ground. But if you measure the voltage it would be more than 14v between alt B+ and ground because there is no real battery to "buffer" the output. Testing it in car is better.

The slip rings could be replaced. I know Bosch slip rings are easily available on eBay not so sure for Denso. Search for it.

Regards,
Amarin.