AC/Tempguage

What is your question?

I replaced the engine in my 2007 Explorer sport trac. The engine temp is fine when running. When I use the AC, the compressor cycles on and off when idling. when I am traveling the AC works fine and does not cycle. However, if I idle for over 2 or 3 min with the AC on the Temp gage starts to climb. Without the AC I can idle for as long as I want and the temp gage will not change. It only goes up when the AC is on and the truck is idling. I also have a new radiator and thermostat in the truck.