AC problems on CLS 500, any help appreciated!
 

Got ac problems on my CLS 500 and would appreciate any help.

The AC worked fine last summer but I have not used it for some time (a few months)

First the "AC off" button turned the light on, and could not be switched off. The AC mechanic checked the pressure that was low, and filled up the system. The fault code was erased from the computer and the light on the AC off button could be turned off. The system was checked for leaks but it seems to be ok.

Still no cold air, only a sound from the system (coming though the air vents) that is the kind from fluid in a pipe. The sound is stronger when the AC is turned on but is still there when I turn it off. When I turn the entire ventilation system off (the "0" button) the sound stops.

The sound stop when I have full throttle, and then come back when I let it up again. It does however not depend on the rpm, and the sound is constant if I drive at high rpm (up to redline) at light throttle.

When hooked up to the computer the pressure in the AC system is about 6 bars and does not change depending if the AC is turned on or off. That might indicate that the compressor is not working, but could also mean that an indicator or a valve is at fault.

My mechanic wants to change the compressor to see if that will help, but since that is a quite expensive operation I would like to be sure that the problem is not somewhere else.

Any ideas about what the problem might be, or how to continue troubleshooting?

Thanks!
/JJ