Pontiac Repair: Automatic Climate Control in a 98 Pontiac Grand Prix SE, No air flow from blower motor

Question
When I first start the car the climate control seems to work fine, any setting (vent, floor, defrost or combinations there of) and using either heat or air conditioning, manual or automatic.  The problem is that after driving about 45 min the air flow seems to decrease and by about an hour of driving there is no air flow at all anymore, even though you can still hear the fans blowing.  If I turn the climate control off and leave it be for about 20 min I will start feeling air blow on my feet again and I can turn it back on, air will flow for another bit but will stop again and I will have to repeat the process.  This isn't such a huge problem in the summer time but I definatly have to get it figured out before the next winter baing I live in Alberta, Canada.

Any suggestions?

Answer
Hey James:

The next time this happens turn the heat to full hot and see if the air flow starts to work. If so I think you may have an evaporator for the a/c system that is freezing up. What happnes in the humid weather if the a/c is on and the system is getting too cold the mositure actually freezes up the evaporator so the air can not flow through it. turning the heat on will thaw it out and the blower will be allowed to flow the air back into the car.. If that is the case either the sytsem is not charged poperly or the control valve in the compressor is bad. See what happens.