I only know one person who has the same 2005 unlimited as me and their's does the same. After turning off the engine with the a/c running, there is sometimes a ticking noise that only stops if I turn the fan to low, a/c off, and temperature directly between hot and cold (temp dial vertical). Regardless of a ticking noise, their is always a sound of released pressure, even if I turn the dials hours later. So I always turn my dials off before leaving my TJ (LJ). Why is this? And is there any harm?