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I'm a little confused about the heater in the car. When you put the heat on why does the ac go on also? Isn't that counter productive? I'm still puzzled how to set the heat. Do I keep it on outside air, recirculate? On my BMW if the setting was set on outside air the car cabin didn't heat up or cool down. Had to put it on recirculate. There was a separate setting for the cabin filter.
 

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In auto setting usually the AC goes on in the shoulder seasons to dehumidify the air for de fogging the windshield. In winter the recirculate setting will eventually fog the windows since your moist breath is kept inside. I believe the AC will not actually run if the outside temp is low enough to freeze the heat exchanger. But that is a guess.
 
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What boblepp said is correct. The AC compressor will not run if the dew point of transfer (inlet from either inside or outside) air is below the dry bulb temperature - hence freezing the condenser. This is automagic within the system, but the point of recirculation humidity buildup can happen if you leave the AC off - leaving it on will allow the inside recirc air to become pretty dry...
 

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In auto setting usually the AC goes on in the shoulder seasons to dehumidify the air for de fogging the windshield. In winter the recirculate setting will eventually fog the windows since your moist breath is kept inside. I believe the AC will not actually run if the outside temp is low enough to freeze the heat exchanger. But that is a guess.
That's very convenient to hear, boblepp. I don't have to worry about my car getting too cold.
 
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