2000 Ford Taurus Front Defrost

Heater problem
2000 Ford Taurus 4 cyl Wheel Drive Type unknown Automatic 150000 miles

My AC does not work because it is low on freon.

I read that when you run your defrost that the AC also runs so that it will remove the moisture and you will have less moisture build up in the front window.

So when I run my front defrost does the AC run. Someone told me that it will not. Yet I have read that it does. So tell me does my AC run when I turn on my defrost? Do I have to worry about using more gas while running my defrost? That is what I am worried about, the use of more gas.

Thank YOU!
Jan