After a closer inspection of the sight glass, I found it was dirty enough not to see through. That'll teach me to look at it without a flashlight!
Cleaned it off and a great deal of bubbles were readily apparent.
So, until I get the car in to an A/C shop, I jumped the electric fan and haven't had a problem yet. Temp sits around 80-85C.

Thanks for all the help.

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1999 E320 (gave to daughter) 250K
1994 F150 (may be the end of its road) 240K
1989 560 SL (Reassembly after paint job) 160K
1986 560 SL (deceased., gave it's life protecting my wife)
1988 300 TE (departed)
1994 945T (still running strong with an upgraded cam) 349K
1986 242Ti (deceased)
1968 GT500KR (under restoration)