In your post "One reason the C-Class sompressors are so reliable has to with the fact that they run most of the time." does it mean the compressor always engaged when AC on? This is what I found on my 94 C220. It works not like those Japanese cars keep cycling the compressor on and off. I check the PBU item 7 by depressing REST a while then press FAN-UP to item 7, the reading goes up from 11.x to 16.x, then goes down to 11.x, repeatly. Seems pressure is OK. I wonder is there another internal switch in AC system to regulate the pressure?
Thanks in advance