Ive got an 84 Blazer. When the a\c is off, hot air blows out of the heater vents. If I turn the fan speed up with it off, the air coming from the heater blows faster. When the A\c is on, it dosn't blow out of the vents very hard. Makes alot of noise, but thats about it. On high, you can't even feel it sitting back in the drivers seat. When the a\c is on, it only comes out of the vents, like its supposed it, just not very hard.