defroster door 99 silverado

[928offroad]

I have a noise coming from under my dash. i removed the blower motor and stuck my hand into the heater/defroster case and if i open the door to the windshield defroster i can get the sound to go away until the door closes on its own and then the noise starts again. It sounds like a electric motor stuck in the on position.Any suggestions as to where this motor is and the difficulty to replace it?

[Red Clay]

Idk what it is but I know what you are talking about. Make sure you have both temp slides equal and the vent selector exactly on what setting you want it makes the noise in mine go away but is a pia. It sounds like an actuator moving back on forth over and over.