Why does A/C come on when using automatic climate control?

[Medic1530]

I have a 2009 Murano LE. I noticed that when ever I turn on the automatic climate control (knob closest to the driver) the air conditioning automatically comes on. I've only had the vehicle since late Dec. 08 and the temps inside the car have been very cold (usually below 32 degrees F) so I know it is not trying to cool the car off. I understand why it comes on when you defog the windows but I'm not hitting the defog button. I'm constantly having to turn the a/c off. I'm sure there must be an explanation for why it comes on automatically.

[KJSmitty]

Most newer vehicles operate this way. The AC is a "dehumidifier". As with most heating or cooling units, removing the moisture from the air facilitates better heating/cooling. No different in your car. When cold, whether on defrost or not, it definitely helps keep the windows from fogging up. You will also notice that when cold, the AC light may be on yet the actual compressor will not run as much as if trying to cool the car in the summer etc.

Most of us do have a minor gripe about it however. :-) Like you, I/the wife just hit the switch once I feel it's not required.

Cheers

[Bunshaw]

The MO is really good with controlling the compressor and using it only as necessary. Nissan approves use of the automatic mode year round. That said, you shouldn't have to keep turning off your compressor.

I leave my MO on auto mode and if I press the A/C button to disable the compressor it remembers my setting between starts so I don't have to turn the A/C off again unless I turn auto mode or the HVAC off. It sounds like maybe you are turning auto mode or maybe the entire HVAC system on/off between starts or during driving perhaps. If you turn the HVAC system or auto mode off it will forget the A/C setting and turn the compressor on whenever auto mode is turned on again. The key is to leave auto mode on all the time and disable/enable A/C as you need it.

[Medic1530]

Thank you both for the reassurance that it wasn't "operator error". I didn't realize the automatic climate control was as efficient as it is. The more I learn about my MO, the more I like it.

Again, thanks for the responses.