Jeep Repair: 05 Jeep Liberty 3.7 v6

Question
Began overheating. Only when ac is on.  Crack in radiator, replaced it and tstat.  Still gets hot when air is on.  Temp drops with heat on. No obvious leaks,noises,obstructions.  Fan is working. Pump a few years old.  No engine lts coming  on.  Anything besides maybe the pump causing this?

Answer
if only over heats when ac is on that means  the system is clogged,  cooling fan inop or radiator is partially clogged.  A bad pump would make it over heat regardless of ac on or not.
Does it also over heat while driving down the high way or will it only do it in stop and go?