Why Does The Airconditioner Compressor Stay On After You Turn On Defroster
Posted in Air Conditioning | Asked on Feb 4, 2012
Below is the question about Why Does The Airconditioner Compressor Stay On After You Turn On Defroster, Seems like if you defrost / de-fog windshield, the AC turns on and lowers gas-mileage… is this something wrong with my car (Nissan Sentra) or is this common effect in most cars?
I guess MOSTLY I want to know why the compressor continues to run even after I switch from “defrost” to … “”regular vent” (not sure what to call it)
“why does it stay on?” … like if I put it onot “regular” and move the heat-selector to “blue” the air that comes out is “refrigerated” and not “normal outside-temp”
There are 4 Answers for "Why Does The Airconditioner Compressor Stay On After You Turn On Defroster"
A/C is on to aid in drying the air that is blowing on window to defrost. Dry air de/fogs better than humid air. There is nothing wrong with your car.
That is normal. The compressor reduces the moisture in the air. The best way to defog the windshield is to turn on the compressor and turn the heat up. The compressor will remove moisture and cool the air, but the heater will heat the air, so what will come out is warm dry air, which is best for removing window fog.
While the compressor does slightly lower gas mileage, I am surprised that you can measure a difference just from running the defogger for a few minutes.
The first answer is correct. The trick is to only use the defroster to clear the windows. Once they are clear, move the heater setting away from defrost. Don’t leave it on to heat up the car.
Its common in cars with airconditioners because if the compressor didnt turn on once in a while the compressor and seals would go bad dry up and leak so it cycles on once in a while but it shouldnt stay on all the time even with defroster on it should turn on and off.