A/C in winter time... how does it works ?

[Claude]

On my car i used to put the A/C in the OFF position in winter time (below 0 deg C or 32F) most of the time here temp stay well below 0C; i realised yesterday that event if i put the A/C ON and set it to blow cold air the compressor does not start unless the outside temperature reach at least +2 or 3deg C (i've got it yesterday just going out of the car wash).

Is it normal ?

[Ross]

I'm pretty sure the compressor wont even come on below a certain temp. by design.
In very cold the sysytem cannot function as the refrigerant wont boil. R-12 @ -21.7*F(-30c) and R-134 @ -12*F(-26c).

[bsell]

I'm pretty sure the compressor wont even come on below a certain temp. by design.
In very cold the sysytem cannot function as the refrigerant wont boil. R-12 @ -21.7*F(-30c) and R-134 @ -12*F(-26c).

Hadn't thought about the refrigerant not boiling.

I've known there is an ambient temp switch in most systems to prevent evaporator freeze-ups and compressor failures due to (oh crap, here it comes) the freon staying as a liquid when it hits the pump (compressor).

See, I knew what you were saying, but never thought about it that way!

Brian