[slartyblarfast]

Dollars to doughnuts your cooling fan is not working. Very common problem.... Too common. With the veh idling turn the a/c on. See if the radiator fan is running or not. It may run slow also. The high speed side may not work but the low speed side might. Easiest way to tell is if the a/c works good sometimes at idle and then sometimes not good.... You can also hear the difference in the sound of the fan.