'90 - 100 Alternator Squeal

[markallen at hannaford.com]

Okay folks, a little help needed here.

Car in this case is a 1990 100 which I've slowly been  working on to put
back on the road. Last fall I had the failing alternator replaced with a
used 110 amp. unit. Winter went by, I didn't move or start the car due to a
bad fuel pump relay which I replaced this spring. Having gotten the car to
run again I find that the dash meter (which I know isn't 100% accurate)
shows output of 13-14 volts. When an electrical  load is applied the
voltage will drop down to the 12 volt range and the alternator belt will
start squealing quite loudly as the alternator takes the load - the drag is
hard enough to stall the car.

I haven't checked the belt for looseness, but since the engine is so bogged
down I don't think looseness is an issue. Thoughts? My mechanic warned me
that the alternator might not last, being a used part, and I believe I'm in
for rebuild or replacement. I'd like to get this fixed as I still have to
replace the c.c. blower, the wiper switch on the column, the roof liner,
and two rear window assemblies. The list never ends...

Mark Allen
'90 V8
'90 100