Well I crawled under and attempted to spin the front (center) portion of the compressor and it won't budge. I had my wife turn the a/c on while I watched, and it looks like the clutch tries to spin the compressor but can't. It doesn't even grind anymore, I just get the burning clutch smell. The grinding must have been the clutch trying to turn an already seized compressor as everyone guessed it probably would be.

I picked up the R134A gauge from Harbor Freight for $49.99, and it really is pretty nice! On a side note, I hooked up my venturi vacuum pump and it registered over 30" HG so I don't know exactly how accurate the gauge is. Either that or the gauge is accurate, but I'm only vacuuming the hose (as opposed to the much greater volume in the sealed a/c system). In any event, I think with the high 95 to 100 degree heat and an idling engine, this venturi vacuum pump should pull enough vacuum to boil out the moisture.

By the way, where is the high side port on the W210 E320? I looked all over and gave up, embarrassed - I can't find it!

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280