Automatic climate control air conditioning

[rwcwilson]

Hi, just a quick question, as a I can't find the answer anywhere. When in automatic climate control does the air conditioning switch off automatically when the interior is at the set temperature or does it just mix the cold air and hot air to reach the temperature? Just thinking about it in terms of fuel efficiency.

[Billc]

does it just mix the cold air and hot air to reach the temperature? Just thinking about it in terms of fuel efficiency.

That's about it! It just does what it needs to do to maintain the temp. Don't worry about the consumption difference, my 2.0 TSI has better consumption in the summer when the aircon is going full tilt to keep my 19C I keep it on auto 12 months of the year btw.

[rwcwilson]

Thanks for the response Bill. Does it still run continuously even if the outside temperature is colder than the cabin temperature setting? Just read somewhere that other systems, e.g. the ford climate control system, turns on the aircon intermittently when it is cold outside just to reduce the humidity.

[andrewr]

I believe the system VW use, with auto and AC on, will run all the time and simply start the AC compressor when needed, I know the AC compressors have a clutch style system so it will disengage when not needed.

Saying that AC compressors have become massively more efficient in the last 15 years, they used to have a fairly large (up to 10%) impact on fuel economy on older cars, now that's down to less than 1%

[mr gee]

I'm not sure which compressor's on our car but some are fixed displacement while others have variable. The fixed displacement would require de-clutching when temperature drops below setting whereas the variable displacement just zeros output until needed.

Like some of you, I just set a comfortable temp and leave it to it's devices.

[andrewr]

Like some of you, I just set a comfortable temp and leave it to it's devices.

Agreed, I think it's more efficient to just leave it on auto and whatever temperature you want and let it do what it needs to do

[rwcwilson]

Great, thanks for explaining that. So as long as it's cold enough outside the clutch will remain disengaged (therefore I assume not using any enginepower) but will continue to reduce the humidity etc.; then when it needs to cool the air further (e.g. summer) the clutch will engage and the compressor will cool the air below outside air temperature. Correct?

Sorry for the specific questions, I just like geeking out on these bits of information