Whilst the AC is on cold, there is a loud, rapid, flapping noise that seems to have its origin at the center AC vent.
If I turn the temperature control to maximum heat, the noise goes away. Whilst the motor is under acceleration, producing torque, (such as pulling from a dead stop, etc.) the noise goes away. However, just revving up the motor while in neutral does not make it go away.
I disconnected the vacuum line at the point where it enters the console beneath the battery and the noise disappears.
All this indicates a defective vacuum actuator somewhere under the dash.
If anyone has experienced this problem or can provide any tips on fixing it, I would greatly appreciate your sharing.
Cheers!
John