Hyundai Repair: air conditioning, hyundai elantra, 2000 hyundai elantra

Question
I have a 2000 hyundai elantra with intermittent air conditioner problems. We never have the outside air flow button engaged and only use the AC button with the dash board vents blowing the AC. Over the last few weeks, we go from having very cold air blowing through the vents to not very cold air. Sometimes this change happens within a few miles of driving to a couple days. We have had the car into our Hyundai dealer, but the two days they had it, it was blowing cold air and they couldn't find any problems. They did a dye check for leaks and then added freon, but the car is still doing the same thing. Do you have any suggestions?  

Answer
First check your coolant level and temperature gauge.  If your car begins to overheat, the engine control module (ECM) will turn off the air conditioning compressor.

Also, it's possible that the evaporator is beginning to freeze up.  There's a thermistor in the evaporator that's intended to cycle the compressor off if the evaporator gets too cold, but if it's malfunctioning, the evaporator may freeze and block air flow and thus you won't get much cool air.

If it's not one of the above two items, I think you're probably looking at an intermittent electrical issue such as a relay overheating.