2010 Cadillac SRX AC problem

ac works ok while driving sitting at a idle just blows warm air higer rpm works no one can find the problem cadillac know their a problem

The problem might be a bad expansion valve.

The expansion valve regulates the amount of refrigerant that enters the evaporator. If the expansion valve fails to the properly adjust to compensate for when the compressor slows down, the pressure drop into the evaporator will be incorrect, and the AC stops cooling.