This just started today on my '19 3500 express extended. Rear AC wasn't blowing at all, on 1, 2, or 3 setting. Drove a bit, then tried the various settings and it started blowing on 3, but not 1 or 2. Then it started blowing on all 3, then went out again. When its not working, as I change the setting from 1-2-3 I hear a definite "click" in the rear AC blower area, like the signal is being sent, but whatever is supposed to "click on" is just clicking instead of kicking on. I feel like I had this exact problem on my '06 suburban, where the rear ac would run only on 4, and sometimes wouldn't run at all. Help or video links would be appreciated. I'm solid with DIY unless its crazy!