Originally Posted by jayadev
generally all the ac has a thermostat which is a rotary knob to control the cooling ,at full position it runs for maximum cooling at intermediate levels it cuts the power to compressor when certain level of cooling is achieved.
so once the cabin is cooled the ac would not operate as long as heat is build up again.instead of that if if we turn of ac frequently the cooling of the cabin and compression part is much disturbed.so it would need to work a lot to maintain that .
in short frequent startup of compressor eats lot of power compared to running one.
so it is always a good idea to maintain an optimum level with ac running automatically
that said.above is not an auto climate controlled thingie Acc is digitally computer controlled with lot of sensors and comparitive measurements of temperature you wont need to fiddle with it as it does what it says.
cars now-a-days do not have a thermostat like the room AC or the refrigerators. ( I do not know about High end cars, but cars like maruti zen, swift santro, esteem, accent, indica, indigo, honda city, manza, etc, dont have it.)
The temperature control knob only operates the hot air vent, so if we turn it clockwise or slide it towards the right, it opens the warm air inlet progressively. The AC compressor is still on till you turn it of manually.
Even in Auto AC/climate control, when we set the temperature for the cabin, the temperature is controlled by mixing warm air when the temperature in the cabin goes lower than the set temperature. But the compressor keeps running.
Cars now have only a high/low pressure cutout.