you have a bad actuator motor or a broken blend door in the heater box, the noise you hear is the skipping of the gears in the actuator motor, the ehating system along with ac use motors to move doors inside the heater box, the doors control the flow of the air and the temp, you will need to locate the bad one by unplugging one at a time, when noise stops you have the right one, remove it by removing screws that hold it to box. with motor removed look at the hole that controls the door, you will see a small square that the motor turns ,this id part of the door hinge, you should be able to turn side to side, this swings door left and right like a rood door, open or closed, if the door swings good then the actuator is bad, let me get a picture to help you located it, you will located the heater box in the location of the noise, behind glove box, try to acess from the bottom of the dash and also remove glovebox,hope this helps, good day
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