Should aircon work in these freezing temperatures?

Horizon81

As we all know (but often forget) a car's air con should be periodically switched on no mater what time of year it is to prevent the seals perishing, ensure the system is lubricated etc etc.

However, should the air con system work in sub zero temperatures? It's -7 degrees where I am this morning and I thought I'd turn it on for 10 minutes or so but I'm sure it didn't come on. Couldn't hear it click in like it normally does or see the tiny drop in revs that occurs when the compressor normally kicks in. From doing some googling it seems some people say the air con should always work whereas others say the compressor stops working around 0 degrees, to protect itself and because it would be ineffective at that temperature anyway. Who's right?

dzug1

Doen't your aircon have a temperature control? Mine can act as a booster heater as well as a cooler.

Horizon81

dzug1 wrote: »

Doen't your aircon have a temperature control? Mine can act as a booster heater as well as a cooler.

No, mine's not climate control, it's just standard air con. On or off. It doesn't help boost the heat, however I'd sometimes use it in conjunction with the heater turned on to help de-mist the windows. Nevertheless, it didn't work today in sub zero temperatures.

oldagetraveller

No, to prevent the evaporator (the bit that gets cold and the air passes through to cool it) freezing amongst other reasons.
Isn't there anything in the car's handbook to warn about this? I know a Vauxhall handbook I had did have a warning.
A domestic refrigerator will not work properly in very low ambient temperature either.

B00st

The compressor for the aircon will have a temperature sensor (or use same one which supplies the info to the ECU and internal temperature display) which will prevent its clutch from activating when the temperature drops too low (usually 3-5°c depending on make of car).

dzug1, how does the aircon in the car heat the air. Car systems only have a compressor, evaporator (cools the air entering the cabin) and condenser (at the front of the engine bay). All that happens if you select a temperature above ambient is that the air is cooled and dehumidified and then heated by the heater matrix as normal.

vikingaero

As others have said most a/c systems shut down at near freezing to prevent ice forming or entering the compressor. Even though you press the a/c button and the a/c light is showing the system won't engage.

Horizon81

Thanks. Given that it hasn't been above freezing (or certainly not above 3 degrees) for the best part of a month now, that's a lot of air con systems that arent going to be getting the regular use they need!

Mark_Hewitt

No, A/C will not usually work below about 5C (engine bay temperature) to prevent the seals freezing when in operation.
Quite often when my windows are steamed up and I've got the blowers on to clear them, nothing happens until I hear the A/C clutch kick in once the engine is warm enough, and they then clear within seconds.

But keep in mind it's engine bay temperature that's important, not outside temperature, so as long as you're engine is warm the A/C should still work even in conditions well below 0.

hethmar

Thats interesting as Ive noticed my air con light on when I havent switched it on during this freezing weather. So you are saying it automatically boosts the heating then?

maninthestreet

hethmar wrote: »

Thats interesting as Ive noticed my air con light on when I havent switched it on during this freezing weather. So you are saying it automatically boosts the heating then?

On the cars I have driven, the aircon is engaged automatically if you set the heater controls to the 'De-mist' setting.

johnnyroper

hethmar wrote: »

Thats interesting as Ive noticed my air con light on when I havent switched it on during this freezing weather. So you are saying it automatically boosts the heating then?

air con does not boost heating all it does is help to demist by removing moisture from the air,having said that in extreme cold temps it will not run to prevent damage from occuring.

in cold weather it is similar to having no air flow over evap coil causing evap to freeze and allow liquid fridge to pass in to compressor.
not sure exactly how a car system prevents running but on a trains A/C it is done by the low pressure switch operating much the same as it would if the evap was to freeze.