Does your car use a compressor speed sensor? That will kill the compressor until you restart the car. An old or loose belt could trigger it. So could a dirty sensor. Of course, so could a compressor that is about to eat its guts.

You may be low on refrigerant, causing not-cold-enough air. If it really has a bad evaporator, that probably means leaking. I don't know how you can say that a car is full of refrigerant, but the AC doesn't work because of a bad evaporator.