Yes, it's normal when you have the heater controls set to defrost. The AC system removes moisture from the air. And thus helps the window to defrost faster.
That's symptoms of the coolant system having air trapped in it somewhere
or
a warn water pump (but unlikely)
or
a clogged heater core.
Or
bad heater control valve.
Sunday, January 4th, 2009 AT 3:17 AM