Oh, well--it was a thought. If everything behaves appropriately when you're in no-compressor mode, the monovalve (and indeed the rest of the system aside from the refrigerant circuit) is unlikely to be the source of your problem. Good luck with it all, and keep us posted--I'm suspicious of a bit of problem with my own, but in my case there's reason to service the monovalve first and then see what's still left over.
'97 SL500, 40th anniversary edition
'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)
SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)