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This is going to be caused by one of the a/c system electric actuators. It you open your glove box and release the retainer so it opens completely, you'll have access back behind that area. It is usually the air inlet/ recirc actuator. It is up and to the right when the glove box is open. It can be others such as the temp which is to the left in the same area. Just follow your ears. When you put your hand on the actuator you will feel it clicking. There are some small screws that hold them on and are a little tight to replace. If it is the air inlet actuator, that is not exactly necessary for cold and warm air, you can simply disconnect the electrical connector to it. The air will still work fine, you just won't be able to change from outside air to cabin air. You could at least do that temporarily if you are not ready to replace the actuator at this time.