if you have the air coming from outside (the dial all the way on the right) and your not moving very fast, it will heat up. if it is recirculating air from inside, it will cool off in the city, but after about an hour of that, it tends to warm up a bit still. that has to due with the crappy r134 coolant used in your air conditioning! if we could only go back to r12, it cooled so much better, too bad it ate the ozone!