I have a 2013 smart, and since I bought it (a year ago), the air conditioner only blows cold when driving. If I idle, the airflow decreases and starts blowing warm/not cold. There's also a humming/buzzing sound, where it sounds like it's struggling somewhere in the car. If I have the car on, with the engine off, the fan blows just fine with no struggle. I've also noticed that if i'm in idle, or stuck in traffic too long, the temperature light comes on. It goes away when I start driving again though. I don't know if these issues are related, but i'm stumped. Any ideas?