2004 Tahoe Z71 loud clicking from inside right rear most trim panel under window

[yellow1053]

had this truck for about 3 years now. runs fine, but tonight, I hear a loud clicking noise from behind the right rear most trim panel under the side window at the tailgate end. I pried the trim away as much as I could to look in, and there is a black box attached to the wall with a wiring harness going into it, and it won't stop clicking (unless I shut off the truck). Anyone know what that box even is??
Thanks in advance if anyone can help.

 

[B-train]

If it's the passenger rear you are referring to, then it's the rear HVAC. Most likely have a blend door actuator that is stripped out or stuck. I did one years back, wasn't too hard.

 

[yellow1053]

Good to know!!! Thanks! (that makes sense, I have already had a blend door actuator go bad under the dash.)