Hi im sorry I know this is an old thread, I have an 04 also ... ive followed as above, clamped off the one hose coming out of the duo and also cleaned the duo and lubed, ... made no difference.
I had the car re gassed a week ago and it was fine for 3 days then went warm,
I went back to the garage and they checked and it hadnnt lost any gas, they did another gas regen anyway ... this time it didnt go cold at all...
The clutch is engaging on the compressor when i press the ac button, you can hear the fan noise change also when the ac button is pressed. The metal pipe that runs behind the headlight is ice cold ...
The garage said the think its a stuck mixer flap behind the dash but they have no experience with MB or crossfires ...
any help or advice much appreciated ...