'89 300CE A/C compressor clutch not engaging

[Dan]

Hi, having researched this from numerous very helpful posts, I appear to be at a bit of a dead end. Some details:

1. A/C did work even though it wasn't the coldest, R12 low probably. (Compressor replaced etc a few years back, only little use since.)

2. A/C recently stopped cooling, compressor not engaging.

3. With engine off, clutch disengaged, outer compressor wheel spins freely with no noise or resistance.

4. Aux cooling fan low speed resistor found toasted, awaiting replacement, but aux fan does work at high speed.

5. Shorted/bypassed low-pressure cutoff switch leads at dryer with engine and A/C on, can hear clutch 'click' but compressor still doesn't engage.

6. Connected +12v to compressor blu/grn wire and also can hear clutch 'click.'

Seems like controls to compressor clutch are working properly but clutch, despite click when energized, is slipping or not engaging? No evidence of excessive wear or oil leak (leaky 103 engine w/valve guide seals) on or near compressor.

Haven't checked clutch gap, assuming with relative newness it was OK.

I've seen a post about using brake fluid or Simple Green to clean clutch surfaces, then rinsed off. Where should this be applied?

Any thoughts suggestions appreciated...