The air stays cold, but eventually stops coming out of the vents after about 20 minutes. If i crank the blower motor it resumes for another 20 mins or so. At this point you hear the blower motor on full blast, and there is cold air near the vents, but no cold air coming out of any vent i can find with any real force. I've seen posts talking about redirection but I can't find the vent that the air is redirected to. I also hear the motor humming along, so I don't think its the blower. Any ideas? this happens on hiway or not. shutting the car off for about 5 mins fixes it for another 40-ish mins of operation.

 

This just happened to me - it seemed to be due to the airbox freezing up... I had ice-cold air coming out (see a separate thread on my A/C fix) which was working perfectly in dry, dry Arizona. I was driving 'cross country, coming into St. Louis with "smoke" blowing out the vents due to the humidity. The air volume out of the vents dropped slowly until pretty much nothing was coming out (and it was getting pretty hot in the car). I parked it for a few hours while going up the St. Louis arch and attending a Cardinals baseball game, and it worked 100% when I got back on the road.

My guess is that the air box just froze up - I can't think of anything else that would reduce the air volume from the vents (I should mention that I also have a brand new blower fan). My fix was to re-insert my airbox temperature sensor all the way - I had pulled it out to fool the compressor into running longer between cycles, putting out air that was right around 32 degrees... guess that was a bridge too far in the presence of humidity. It might be helpful for you to monitor the output temperature at the vents to see if your system is REALLY cold - you could have a calibration problem with your airbox temperature sensor (a high class problem if you live in a very dry climate).

 

Year and model of the vehicle would help. A lot of the tunes what happens is the gap in the condenser clutch gets too big over time and shuts off the clutch