Here is a good one. I have a 07/01 build date s500 and all of a sudden the a/c off button stays illuminated and no ac compressor engagement. The TSB is to switch the freon algorithem to inactive and clear fault codes. Did that and the system now operates normally but no compressor. A field tester shows some activity in the compressor power wire when its turned on but the clutch seems to allways be engaged. The freon level is good and no changes occur when the compressor is energized. The guages read 100 on low and high sides. Disconected the battery and still no compressor. Im wondering if a valve inside the compressor could get stuck or break without any indication or noise. HELP!!!

 

Well ,Im waiting for any reply? We are subposed to communicate here arnt we?

Reguardless of the lack of info from this group I have figured my problem out. It has come to my attention a problem with the design of the compressors for many MB models from 99 to present. A small series of reed valves internal to the compressor can instantly break and cause a catastrophic failure in the Denso compressor. No external signs are visable but the unit will trigger the AC Off light on the dash and not let it go into the full cool mode. If pressure readings are ther same for both high and low sides than the valve has failed and a new compressor will need to be installed. Do not buy used! The reed valves go bad over time and dry out when stored dry. Best of luck to all who could use info.