The AC automatically comes on when you turn on the defrost, to dry out the
air directed at the windshield.  The theory works like this.  First the AC
cools the air, which then has the ability to carry less moisture, so that
much of it condenses and goes out the AC drain hose.  Then, the heater coil
heats it up, resulting in warm, dry air, which is exactly what you want for
defrost purposes.

My 1999 Civic does this.  When I turn on the defrost and the heat, the AC
light comes on every time.  It is supposed to do that.

Earle

Ummmm..........."this sucks" and "sumbody" tells me that you're,
what--18, 19 years old?

Please know a few things:

a) air conditioning and heat are not mutually exclusive

b) air conditioning does not cool the air as much as it DRIES the air

c) with the controls as you say, you are getting DRIED, HEATED air to
the windshield

which is *exactly* what you need to defrost the windshield.

Put your hand up there.  The air IS heated.  It's also "air
conditioned," which is to say the AC is on and is removing moisture from
the incoming air; that dried air is *then* heated by the heater.

Simply putting hot, moist air up to the window will do exactly nothing
to defrost the window.

(hint:  "defrost" means "to remove moisture")

Wait for the engine to warm up.  The A/C comes on to dry the air before
it hits the windshield.  Otherwise, sending moist air to the window will
cause frost/fog to form on the inside of the windshield as well.

marco