not blowing enough air out of vents
 

Just bought a 91 chevy 2500 5.7 and when you turn the air on it doesn't seem like it blows enough air out of the vents. If you turn it to the floor it seems to blow alot more air. It doesn't matter if I set it to heat or A/C it also doesnt blow well out the defrost. Any suggestions much appreciated.

It is either the door in the box jammed or the actuator (most likely) on the side of the box went bad. Look on the left hand side of the airbox near the floor, just above the tranny hump. The actuator is there attached to some linkage. Take the atuator off and see if you can move the door freely through the linkage. If you can then the actuator is bad. Replace it and you should be good to go. I have had to replace that same actuator on 2 trucks I had.

mine did that too. i had to replace the heater-a/c control unit. it was like 115 new from the dealer or 45 from the junk yard.