Hello, My 2010 Prius today AC started blowing cold air as usual in when I turned on the car. I sent a couple of text and then started to back and drive it immediately went from cold to hot. When I got to the stop sign on my street and came to a full stop it started to cool off. A couple of cars passed it started blowing extremely cold air again. Soon as I pressed the gas it went back to warm. Any ideas?