When I turn just my fan (no air conditioning) to have it blow on my face only, it makes a loud buzzing noise (not a rattling noise) that continues until I turn it off that setting. If I turn the fan to both face and feet, it goes away. This noise also happens sometime for a short period when I start the car, even when the fan is on the face and feet position. This just started about 3 months ago.
My car has 99000 miles.
My car has an automatic transmission.
This may be a sign of a faulty blower motor. As you might know, these have electric motors in them that wear out over time and will begin to make squeaking or grinding noises as the bearings begin to wear out. The electrical contacts may also wear out causing the motor to fail. In some cases they may show signs of wearing out by making the noises as you have indicated only at certain speeds, but will progressively get worse at all speeds as they eventually wear out completely. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your blower motor.
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