Why does the air conditioner compressor cycle with defroster on.

[newjeepowner]

I have noticed this also on my 2002 Grand Cherokee and 1999 Cherokee. When I turn on the windshield defroster i can hear the compressor cycle. Why?

[87xjco]

Helps remove moisture from the air

[MuckSavage]

Almost all vehicles do that....The A/C systems stays lubricated by the compressor running. This allows distribution of the lubricant even when the A/C is not on. There's alot of recommendations like "run the A/C for 5 minutes per month, even in the winter"

[1096xj]

Like 87xjco said, the ac dries out the air. Thats part of what makes you feel cooler. It is just like low humidity outside feels cooler.

[newjeepowner]

I understand about removing the moisture in the summer when your AC is on. But when it is 10 degrees outside and you have ice on your window. Why would you want to remove the moisture in the air. All you want to do is blow warm air on the windshield so the ice melts.

[XJ Un-Limited]

There's still moisture in the air, ever notice the rest of your windows fog up inside when it's cold outside and your sitting inside? The moving air helps, dry air helps even more.

[kennzz05]

there is a low pressure switch and a low ambiant switch that prevent the compressor from running at temps below freezing so you will only notice the compressor cycle at temps above freezeing

[DenLip]

I understand about removing the moisture in the summer when your AC is on. But when it is 10 degrees outside and you have ice on your window. Why would you want to remove the moisture in the air. All you want to do is blow warm air on the windshield so the ice melts.

Well, as already mentioned... DRY air eliminates the fogging INSIDE while you're trying to defrost the outside...

As a guy who parks in an unheated garage... most of my fogging is INSIDE, when I breathe on the cold windshield.

Den

[newjeepowner]

thanks to everyone who explained this too me. I have never notice my air conditioner compressor run before until I got the 2002 GR Cherokee.

[kennzz05]

as was mentioned earlier most cars probablyfor the last 20 yearshave had that feature all american cars have anyway