2004 Chrysler Sebring sedan heater issue

Noticed my windows would not defrost last week, and then when I got into the car the air was blowing cold. However, as I drove down the street the air warmed up and worked fine. Same problem continues. We thought it might be a problem with the thermostat being stuck open. Went ahead and replaced it, but that was not the issue. The thermostat when removed was fine. Any ideas?
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Answers
It was below freezing this morning at my house, and the inside of the windows on my hatchback were actually frozen over because we had picked up a Christmas tree in the rain on Saturday and the inside of the car was still really humid. It took roughly the time it would have taken to drive a half mile or so before the defroster air was warm enough to start clearing the windows. Perfectly normal.
Points for ray80!!
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