check for a vacuum leaks. Is your heater stuck blowing out the defrost only? If so; you have a vacuum leak; fix that and more than likely it will fix your cruise control too. There is a line that plugs into the side of the intake around the throttle body... check that; it might have come off, just plug it back in.
Anyway... vacuum loss is probably the culprit. Your jeep is too new to be anything else.
