2003 Sentra A/C cycles on and off with heater on in Canadian winter

[clarkt]

Any ideas why my A/C is cycling on and off with the heater on?

The manual says at above 47 degrees in defrost position this is normal with the fan on and the A/C switch off but my A/C goes on in sub zero temperatures at all dial positions with the A/C switch off.

Afraid to take to the dealer without some idea what might be going on.

[scoobysteven]

My 2002 Infinity G20 does the same. I do not think it is an error. I think the thermostat is just trying to keep a constant temperature and when the heater makes the cabin too hot, the AC kicks in to bring it down a tad. I don't like it either, I think it is stupid.

[Buzzman]

This is perfectly normal operation.The main reason it is programmed to do this is to keep the A/C system lubricated and pressurized. If the A/C system is off for 5 months during the winter, it is guaranteed not to work in the spring when you finally need it.The secondary reason is to take some of the humidity out of the defrost air to prevent your windshield from fogging up on the inside.Car manufacturers started this programming back in the 80's.I remember buying a new '88 Chrysler minivan, and my A/C compressor would kick in when I had my defrost on in the winter. I took it back to the dealer because I thought it was broken. Turns out it was programmed that way for the reason I explained above. Every car I've owned since then has been pretty much the same. Happy motoring.