Couple things I didn't see covered (or missed if they were) use a thermostat to cycle the Compressor. Several people saying to hit the A/C switch when so equipped. Just wire a thermostat in line with the A/C button.
One thing I have proved in all the vehicles I have driven with frequency is when you live where it is hot the A/C is a better choice then open windows on the interstate. For work I drive a Chevy Express. I get a full MPG better average at hwy speeds using the A/C then I do with the windows down. I often make 200-300 mile round trips in a day and I can average 17.1 mpg with summer blend fuel on that vehicle. I have seen simular gains with the Ford Transit connect I am doing a review on for the company I work for. Speeds under 40mph its a wash windows verses A/C unless you are in gridlock. Then of course widows open wins if you can stand the heat.
"Your air conditining is operated by an engine driven compressor, then two "radiators"; a high pressure, hot one that is warmer than the outside air, and a low pressure, cold one that is cooler than outside air."
