My 01 7.3 was not blowing the air through the vents just through the top defrost vents. So after some research I purchased a vacuum pump that goes in the engine bay passenger side. A/C was working although when I would put "max" a/c the air would blow through the top again.. I'd figure it was a bad line somewhere.. anyhow now the pump I guess went out again. AC blowing through top and I don't hear the pump when I turn the ignition..