96 cherokee that only seems to over heat on warm days with AC on. If I am over heating and turn heater on engine will cool down and run wo a problem. On warm days if I leave the AC off it will run pretty normal. With AC on sometimes OK and sometimes not. Water pump and heater valve replaced 6 months ago. How do I tell if radiator is the problem? Other than circulation or thermostat any ideas or troublehsooting steps? Thanks!