Clunking dash

[Dean Lyle]

Hey all, I'm getting a rhythmic sound coming from the dash on the passenger side when I turn the key to on. It speeds up when the engine is running. Happens when the defrost is selected. Take a listen and let me know if you recognize it plus a fix if you know. Thanks

2000 2500 Silverado LT EXT Cab short box 4x4 6.0L w/153k

My recording 1.wav

[jay webb]

sounds like an actuator is the issue. they open/close doors in the ac case to direct air flow. or maybe a broken door