Hello, I am aware that the A/C compressor wont kick on when the outside temperature is bellow 5 degrees celsius. I find that rather odd as I often need to defrost the windows, and without the AC it takes much longer. Can someone explain to me why is it like that? Why cant I run the compressor on cold temperatures? Is there any way to bypass this, and turn on the compressor? Thanks in advance.

You want some heat to de-frost / de-ice, Air Conditioning is not what you are after.

 

You need heat into the engine, coolant up to heat, thermostat open, engine oil heating and heat out the heater.

Because to dehumidify the air you need a surface colder than the incoming air so the moisture can condense on that surface.

 

There is a limit to how cold you can get the evaporator because otherwise it would freeze up and you would get no airflow.

 

So the answer is yes, you could bypass the system, but you wouldn't want to as you would get no airflow at all once everything was frozen solid.

What he said, with the additional note that the ice build-up can destroy the condenser.

Best to not use the compressor at this time of the year at all. Yes if the temperature is high enough to allow it to run it de-humidifies to stop moisture hitting the windscreen - however of that moisture removed a residual amount remains in the system which then deposits on the windsreen next time you start the car! 

 

It's best to get the car thoroughly warmed through so that any moisture evaporates off - then don't allow the compressor to kick in (be air con off, econ mode etc...).

 

My self, if it's going to be frosty/v cold, I put a fanheater in the passenger side front footwell fed via an extension lead that I can turn on first thing in the morning which I turn on before having my breakfast - lovely an toasty when I get in the car. NB I always tie a duster to the top of my steering wheel to remind me the car is still plugged in to stop me driving away still connected to the national grid!

 

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On 25/12/2019 at 22:28, zejdkoco1 said:

Hello, I am aware that the A/C compressor wont kick on when the outside temperature is bellow 5 degrees celsius. I find that rather odd as I often need to defrost the windows, and without the AC it takes much longer. Can someone explain to me why is it like that? Why cant I run the compressor on cold temperatures? Is there any way to bypass this, and turn on the compressor? Thanks in advance.

If it’s convenient then open both front windows about 30mm. The flow of the air will defrost the windscreen quicker. I do this when it’s frosty and works much quicker then when it’s all closed up. Hope that helps?