Variable Displacement AC C-Class
 

Hi:
I have a 99 C class with the variable displacement AC compressor.

Usually this compressor is always on. My question is it possible for it to turn itself off at low outside temperatures?

This morning it was in the mid 20s(F), and after returning from a thirty minute highway spin I noticed that the clutch was not turning. (I was checking the windshield washer fluid before putting it in the garage).
After engine shut down(and sitting for about five minutes) the compressor was spinning again.

The last time I noticed this was after a highway spin at -8F.

From what I understand the compressor always spins to keep the evaporator temp at a constant temperature (I think its 32F).
So in theory the compressor may stop spinning (compressing) if the air moving through the evaoprator (especially at highway speeds) is already at the predetermined temperature.
What do you think?

The A/C compressor runs when the climate control is in Automatic, Bi-Level, or Defrost mode. The compressor does not run in Economy mode. At least that's the way GM did it when they used the V5 compressor. I suppose it's possible that MB shuts the compressor down under certain circumstances, but the whole idea of variable-displacement was to do away with a layer of electronic control.