I've been talking in another forum about this but figured more eye/ears couldn't hurt. This is a 5.3 4x4 Z71. The video I'm sharing is right after start up. Seems to sound the worst when started after the engine has cooled. It sounds like its coming from under the dash, center or possibly passenger side, its a bit hard to pinpoint. I don't seem to be able to hear it when under the hood. Its not constant, seems worse with the AC on but will do it sometimes but for a shorter duration when AC is off. I hear it off and on while driving, I've noticed that when its happening while driving if I turn the AC off it stops. I've pulled the blower out and its clean. Also with the blower disconnected it still happens. We've considered blend door or something along those lines but in my experience that typically makes a different sound. The AC does work well and blows hard from both front and rear vents. Fluids all look good, clean no funky smells and appropriate levels, oil pressure and engine temp look good.

Appreciate any ideas you all might have. I'm sure I've left out some useful information just let me know and I'll fill in the blanks.

Recording of sound


RPO codes

 

sounded like a blower motor but I just read it happens when disconnected. Maybe flow through heater core?

 

From what I've read issues with the heater core usually result in a gurgling sound. I may have to bite the bullet and have it diagnosed by a mechanic.