A/C began to blow warm air and temp began to rise. when I let it sit for 20 minutes ac blows cold again but only for a short time.

Hi Chris, sounds like your thermostat may be worn and not closing all the way which would cause your engine to run cool at times. If you have a temp gage it should tell you if the engine is actually warming up or not. If not I would replace the thermostat.

Have your thermostat checked, sound like it is not working when cold.

mine does the same

TX valve freezing?

Two things to check. First I would make sure that the front of the car, where the condenser is, is clean. Make sure you have air flow threw the condenser and radiator. Second check the freon level. The pressure on the low side should be 40 to 50 psi. The condenser is the part of the A/C system that releases the heat, the cooler you can keep this the cooler the inside air will be. That is why it is important to keep the bugs cleaned out of these.

your ac compressor is freezing up try not putting it on cold all the way. put thermostat towards the red jus a lil but still on the cold side to see if that helps

It sounds as if you have an ambient temperature sensor that is either shorting out when it gets wet or either the water is acting like an insulator and sends an incorrect reading to the body control module. You may want to contact BMW to the specific location on your particular year and model. As location will vary with model and year.

u have a temp door accuator motor shorting out

too much freon is the same as not enough freon

Have an 04 mazda6 as well, AC seems to be the cars weakness. It takes 15-20 minutes till my car is ina driveable condition (Phoenix, AZ)

Take it in for a tune up, but I doubt the AC will be any better

Sounds like a compressor problem.