what's more fuel efficient?

[BlahBlahYouToo]

i would think that turning off the AC is more efficient than having it constantly cycle on its own.
if i'm not mistaken, the compressor never stops cranking. the HVAC system just regulates how much of the cold air goes into the cabin. is that right?

how much wear/tear is done on the AC unit by constantly turning it on/off manually?

 

[AnnonUSA]

The compressor pulley is an electrical clutch assembly that engages when cooler air is called for by the Cabin thermostats. The compressor clutch can also be disengaged when the engine needs more power, like on hard acceleration. When the Clutch disengages, the compressor is not turning.

 

[thomsbrain]

My car seems to cycle the A/C on and off even when in full auto mode. It always comes on when you first start the car to make sure the windshield is clear of condensation, but after that it doesn't just stay on all the time unless it truly needs maximum cooling. In moderate weather, you can vaguely feel the compressor engage and disengage at stoplights. But this is true of almost any car with A/C, not just those with climate control. On lower fan settings, the A/C will cycle off occasionally.

I don't think you'll do much more wear and tear by doing it manually, but I highly doubt you'd see any significant benefit.

 

[LTC8K6]

The compressor only runs when it needs to. It is controlled and runs proprtionally according to how hot the air is and what settings you use. Just like your home air conditioner does.

For example, it is not running a lot if you have the A/C set on recirc or max and the cabin has already cooled down.

The computer will also shut the compressor off if you ask for a lot of acceleration.

On older cars, a WOT switch would shut off the compressor at full throttle.

 

[LTC8K6]

It is likely going to be much more fuel efficient to let the system maintain a comfortable temperature on recirc or max. This way the system is recycling ~75% of the cabin air, which has already been cooled, and the compressor should run a lot less.