I live in the UK and therefore rarley see the sun, I havent used my AC for at least 6 months now due to the cold, rain, sleet, snow etc.. But my friend told me you should let the AC run for a little while every week so that it doesnt mess up!
Yes. The seals can dry out when it's not used for long periods and 'pickup' when it finally is causing wear to them.
I have another UK made car with AC which runs the compressor when you select demist - as well as making sure it's used during the winter months the AC helps dry out the air.
The a/c compressor runs when you set it on defrost, so this means that most a/c compressors run year round. unless it's very cold. If anything you should set your heating system to floor or vent, that way the compressor will shut off and you'll save money on gas.
I certainly don't know about the actions of older BMWs, but all cars designed in the US use the A/C to clear the windshield during cold weather. They have used that technique for well over 30 years now. My first car with a factory equiped A/C was a 1967 Ford, and it definitely used the A/C in that manner.
There is a difference between normal AC and climate control systems. All of the climate control systems in cars I've owned - all the way back to a 1978 Ford - took complete control of all settings, including the AC compressor operation, when set in full auto mode.
As others have said, an often overlooked function of any AC system is a dehumidifier. That function is equally important in house AC systems, as well as cars.
On Wed, 14 Feb 2007 21:04:46 -0500, Dean Dark waffled on about something:
Hmmm, very curious.
Okay, well I think I know why I have never seen it, and "s" has seen it everywhere since the ark. He's in the US, I'm in the UK. Given that American cars tended to have big engines, I guess the manufacturers weren't really bothered about the extra load of the compressor being engaged when you went to demist the car, whereas with a little Euro-box it was deemed the driver should decide if he wants to loose half the engine power!
The '94 E36 I was referring to did have climate control (all be it the early 4 knob flavour, not the digital one that came along later), and the A/C was something extra you decided if you wanted or not, the way it functioned was more of an add-on than an integrated part of the system. I know for sure the A/C didn't come on automatically when I tried to demist the screen because I used to make a point of manually turning it on. If I forgot, it took ages to clear.
On Wed, 14 Feb 2007 19:19:01 -0600, "s" waffled on about something:
S, I'm not trying to have an argument here, I'm just saying that what you are saying is a broad generalisation, which several of us here can disprove from out own experiences.
To the original poster, press the button every week or two, a/c will help demist the car, and use of it will keep the seals in good shape. Your car may, or may not do this for you already, without knowing the model/age we can't say for sure, so it's safest for us to say press the button.
Right - I've just done some checks. With a fully warmed up engine, selecting AC on my climate control E39 causes the rev counter to rise before returning to near normal. The engine note also changes slightly as it's now under load. Selecting defrost does no such thing - so on my car at least it's not engaging the compressor.
That's funny, on mine the air con makes idle speed increase a lot and stay there. I've not had it on for long but it goes from (if the tach is linear at that point) ~250rpm to about 750.
The demist button does not appear to run the air con on mine either. Pity really as it sounds like a good idea, to keep it exercised if nothing else.
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