A/C Tapping 06 Impala

2006 Impala LS makes a tapping sound whenever the AC fan is turned off while in recirculate mode. It lasts approximately 30 to 45 seconds. No problems when set to outside air.

The noise is from behind the glovebox. When glovebox is lowered you can see what a light colored bellows attached to a black plastic ring moving up and down.

Mode door actuator problem usually causes this.