Grand prix won't blow air hot or cold from vent.

Is the blower motor running but not moving any air or does the blower not run at all? If the blower does not run at all its likely the resistor located in the ductwork on the passenger side against the firewall inside the car.

Althou a b#@!$ to fix if you're tall, gonna have to lay on your back in the passenger seat with your legs over the head rest and head under where the glove box goes to fix it! This is one of the fixes I had to do! Remove your glove box...open it and should pinch out of the hinges...grab a ratchet set and remove your blower motor...its 4 bolts...then unplug it...plug in a New/used one and bolt back in place... What caused mine to go out was a leak in my windshield...even if your passenger side floor hasn't gotten wet, it cud still be the cause...just the rain etc. That pools into your blower motor may evaporate before overflowing and spilling onto the floor... The leak is an easy fix too...I had to research and figure out the problem myself after 3different shops were stumped! Lift your windshield wipers...use a screwdriver and remove the clips holding the black plastic vent under them...there is a rubber rain spout that notoriously falls off...find it, aim the spout towards the passenger door and use some clear silicone to KEEP it in place...then run a line of the clear silicone along the bottom of your windshield...replace the vent, resecure it...drop your wipers back down...this was the first time I had EVER fixed my own car and took me all of 20min to fix my leak on the passenger side floor...2years later, no problems!! I wud absolutely suggest at least checking if the leak is what caused your blower to go out so it doesn't happen again...