Happened the other day. I was stuck in traffic and all of a sudden the AC was putting out hot air. Once I started moving again, it worked fine. Now, whenever I start the car, I get hot air until I start driving. Compressor?

 

The 1st thing I would check is to put a set of gauges on the system and check it's pressures. If OK then you need to go back into the the control system which I believe needs to be diagnosed with the dealer link.