Try turning the recirculation on and wait and then turn it off. See if the noise changes?
March, 19, 2012 AT 11:00 PM
Changing any of the settings on the heater or AC does not effect the noise.
March, 19, 2012 AT 11:05 PM
Your going to have to trace it down to its source and we will go from there.
March, 23, 2012 AT 7:51 PM
Sounds like the motor that controls the recirculation when it starts to go bad it wont cut off it just keeps going a quick way to find out if this is the problem is to take the piece of plastic off of the front of the windshield where your windshield wipers are and then look in the little vent and see if you can see the piece of plastic that is moving it will be on the passenger side I had the same problem until I took out the passenger airbag and unplugged the motor in recirculation the pic is the sensor and the flap that is probably making the noise
March, 23, 2012 AT 11:15 PM
Also I have had customers with broken recirculation doors cause the same thing to happen where the recirculation servo keeps running.