Knocking Noise

if the noise is happening when you turn your temperature from hot to cold or cold to hot that would be your blend door actuator

It’s the blend door actuator servo. The plastic gears inside are stripped out. No big deal. Remove the glove box to access it. Unbolts with two bolts, unplug wire is all there is to it. If you don’t want to replace it just yet simply unplug the wire and the tapping will stop but of course the fresh air intake door won’t work.

how to fix clicking noise in chevy impala 2012 driver side