I bought a AMM from an internet site (Parts Bin for $226) & took it to the Volvo dealer for adjustment. The service rep said they couldn't get it adjusted & added he'd never seen a good 'aftermarket' AMM (or alternator). Theirs is $500+. It's a new BOSCH AMM. What's the difference? Should I try another mechanic? Thx

That one you got from the parts bin is listed as a new Bosch.
I've got news for the dealer... that IS a factory part, not a cheap aftermarket piece, and there is no adjustment on that one, the computer does all the adjustment , just plug it in and go,( I also have a '90 )
There is no difference in the Bosch you purchased and the one that they are trying to sell you except the price.

You know the old saying that goes something like" what I've got to sell you is what you need, and the other guys isn't any good". If the part you ordered is Bosch, and it's a direct replacement for your application, then I think I'd find a second opinion. It's possible to get a bad one from the box, but I think I'd ask someone else just to be sure. You might want to contact where you got the new one and ask them if they have any history of bad ones.
Good Luck!
Tim '87 740

What did you want to get adjusted? 90 240 has LH 2.4, and there are no AMM adjustments. You simply plug it in. If the unit you got has an adjustment screw, it's the wrong one.

According to the Bosch catalog the 1990 thru 1993 share the same AMM
P/N 0-280-217-001 - these are non adjustable. What is the part number on the AMM unit you are trying to adjust?

the part # for the AMM I installed is 280-212-016 (B3130-63452). The car runs a little rough & black smoke is coming out of the tailpipe. Parts Bin also sells another unit #280-217-001 (B3130-27570). I'm guessing I got the wrong one??

AMM part number 280-217-016 -- on my '90, '91, and '92.

Two of these are turbos and the third one is a B234F. They all share the same
AMM part number. I swapped one of them from turbo to B234F during a trouble-
shooting episode and it worked fine. My bet is that the B230F uses it too.

There is no adjustment on this AMM.

LH 2.1 used 280-217-007 and that one did have an idle adjustment. This was used from '86 to '89 on the non-turbos.

If it were me I would suspect that the dealer is either wrong or less than honest.

Does the car run with the new part?