The blower motor starts to draw more amps as it ages. Enough so, that MB issues a TSB about it and a fix kit. The fix is a 30 amp aux. fuse holder added outside the fuse box. I'd lube the motor on general principle.

I'd say you're #'s sound good for the alternator unless you're talking that kind of drop at 3000 rpm.

The blower motor bushings aren't the motor brushes.

The bushings are at either end of the motor casing at the shaft.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)