Take a look at your owners manual to see how the front defroster works. It should tell you how to turn it on and how to tell if it's working.
The basic idea behind the front defroster is that instead of just blowing air up on the windshield, it turns on your a/c compressor so that the air is dry air, therefore clearing the windshield. You can choose the temperature, it doesn't mean that you will have cold air just because the a/c is running.
I've seen some vehicles where the a/c light actually comes on when the defroster is running so that you know it's in defroster mode. You'll have to check your owners manual to see if this is true for your vehicle.
〉 Answered on Jan 4th, 2007 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines