Noises from A/C if dials aren't turned off after (or before) turning off engine

Dawgrit

New Member
Joined
May 2, 2021
Messages
6
Location
Florida
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?
 
There will be a pressure release sound under the hood as the pressures equalize in the refrigerant lines and that's completely normal.

If the sounds are coming from within the dash, it's probably related to the vacuum hoses and actuators that move the various doors that direct air flow to the right places, and if they're not perfectly sealed maybe there is some motion in the actuators as atmospheric pressure floods into the system. Mine is an 06 and I don't think it makes any noises, but I'll pay attention next time I drive it. It's possible you might have a tiny leak in the system that holds vacuum well enough during operation but bleeds off once the engine isn't running.