2004 CLK 320 A/C On/Off operation
 

Hello,
I have a 2004 CLK 320, which I purchased used several months ago. I am still getting familiar with some of the controls. I am a bit confused about the A/C OFF button functionality. The owner's manual indicates that hitting this button will turn the A/C compressor off. When I have the cooling system set at a low temperature (it's hot outside), I have both cooling zones set to AUTO, and I hit the A/C OFF switch, it is clear that the compressor is still running and very cold, air conditioned air continues to come out of the vents. The dealer told me that this is normal - that the compressor always runs in this model - this contradicts logic, and the owner's manual. I would assume there is a way to run the cooling system in an economy mode, similar to selecting VENT on older cars. Can someone enlighten me on this issue?
Many thanks,
John

After you push the A/C OFF button wait a few minutes and see if the air is still cold. The compressor can take up to two minutes to reduce it's output and then the evaporator temperature will need to stabilize. Remember that MB has used variable rate A/C compressors for a few years now, so the "clutch" always appears to be turning.

Thanks for the input. I believe I have tried waiting a couple of minutes, but I will give it a shot again.

I believe that some of the newer A/C compressors do not have a clutch that allows them to disengage the compressor from the drive pulley, these compressors can never be completely turned off.

However, they are variable displacement and can vary the displacement to below 5% of maximum allowable displacement. Hitting the EC button should take the compressor down to minimum allowably displacement, which is the closest to off that it can get. Therefore, you should still get a hair of cooling out of it.