My car runs at normal temp even when its extremely

My car is a 2000 Ford Crown Vic P71 with 240k miles on it. I always service my vehicle when due. My car runs at normal temp even when its extremely hot outside and in stop and go traffic, unless i turn on the a/c, then it gets hot, i hear the fan kick on, and i have noticed that when its on max a/c it doesnt seem to start getting warm as fast if at all. but normal a/c even out on the freeway it gets hot. it has never overheated to the point of shutting down or blowing antifreeze, i always shut the a/c off before it gets to that point. It has a 140 thermostat in it, would a 180 work better in the Phoenix heat? If not, what should I do?