Nissan Repair: A/C Problems on 1988 300ZX, nissan 300zx, vacuum lines

Question
1988 Nissan 300ZX non-turbo w/179,000 on the odometer. I just recently bought the car from my wifes uncle and he said the ac worked sporatically.I had the ac drained down because I could not get it to work and recharged with freon. It blew cold for about 2 minutes out the vents on the dash then started blowing hot air out the defrost vents and floor vents. It has blown hot air constantly out the defrost vents even when nothing(ac/defrost) is on. When I turn the ac on it sounds as if the compressor comes on but it continues to blow hot air out the defrost vents.Any help would be appreciated

Answer
Billy,

Check the control panel and vacuum lines to make sure that they are connected correctly.  It sounds like the system is working but the vents change direction.  You are probably looking at a defective vacuum motor that controls the defrost/vent/floor door.