Climate Control System - Tapping noise

[irisman]

I have a problem with my Climate Control System in my 97 NSX-T. When I turn it on, I hear a clicking taping noise – it sounds like a plastic (not a metal) tapping noise. I hear this noise on each possible set-up, except on the following mode – When the main air flow is divided between the floor vents and windshield defroster vents. Please help!