Check to see of the belt to your air conditioner is loose or the compressor is broke or even if the fan carrying the air to the dashboard may have a blown a fuse.
The air conditioner should not stall out the car if it does the problem is most likely from a bent or frozen pulley. Depending on the car you can wither replace this or bypass this with a smaller pulley.
Most likley by stalling you mean the blower motor is not turning to fix that you will need to go to the junk yard and get a new blower motor. Take apart your entire dash and install it. Put your dash back together and your set.