Climate Control - Auto Function Question

[F1ADAM]

Peoples, not a biggy but a head scratcher, for me anyway.
Does anybody know why when I switch to Auto Climate Control on, the air conditioning comes on as well? It happens even if the temperature is set to warm or hot (22+).
Does Air Con heat air up as well as cool it?

 

[Jimmy Gee]

Simply YES, not sure exactly how it all works but that is the norm.

 

[noxas]

When you turn on Climate Control the car will try to maintain the temp you set with the right hand control [the one with the Temp on] so if the temp is 20c in the car and you set the control to 18c the air con will cool the car to 18c and maintain it. If you the set the control to 25c the air con will turn off and the heater will come on full with full fan to boost the temp to 25c. You will also note that air comes out of all vents at the same time and the light on the vent control [the one on the left) goes out. all vert clever but really only works when the roof in up and the windows closed.

 

[F1ADAM]

Thanks Jimmy. Good to know its the norm.
Does anyone have any deeper knowledge of why air con is required for warming the air?

 

[spanna2000]

On my late 04 car:

The AC light is always on in the standard full auto mode. When the AC is running the outside air is cooled as it is drawn into the heater system and then after cooling it is re-heated. This is a good idea because the cooling process condenses the water vapour in the air, the condensate then drains out of the heater system. The air going forward to be re-heated is drier than the outside air. This drier air helps de-mist the interior of the vehicle (this is why the de-mist button also turns the AC on). The auto system will turn the heat input and the fan speed up and down to hold the interior temperature of the vehicle at the desired temperature.

You can manually turn off the AC and the system will remain in auto mode - the fan and heat input remain under the system control but if it is too warm the system cannot cool below the temperature of the outside air.

You might want to turn off the AC if you are worried about the fuel consumption or power drain. The compressor puts an additional load on the engine. I have not been able to observe a difference driving with a full tank with AC on and then another with it off I get similar MPG. I sometimes turn off the AC because I don't like the dried air effect all the time.

I have read suggestions that the compressor will switch on and off automatically as required but that doesn't seem consistent with my experience - the compressor is working even when the temperature outside is low - I think I know this because the air has been dried and is de-misting the car better than when the air AC is turned off.

I am not sure if the Auto mode controls the airflow direction. In other cars I have owned the system directs the heat to the floor settings when the car is cold. As it warms up more air is released to the face level vents. Not sure if the Z4 does this.

 

[CoupeChief]

I am not sure if the Auto mode controls the airflow direction. In other cars I have owned the system directs the heat to the floor settings when the car is cold. As it warms up more air is released to the face level vents. Not sure if the Z4 does this.

I think it does.

 

[F1ADAM]

Thank you Spanna for your detailed explaination. That made a lot of sense, particulaly the part about the system not being able to cool by more than the outside temperature if the air con is off.
Thank you also everyone else too for your input.