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Q: No air in vents or defrost

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The blower motor does nothing unless im going over 40mph then heat defrost and ac all work doesn't seem to make a noise when it does work but i can't control how much or how little comes out

My car has 200000 miles.
My car has an automatic transmission.

A: Hello. If there is no air coming from your...

Hello. If there is no air coming from your vents then there is likely an issue with the blower motor or circuit. The first thing I would do is check the vehicle's fuses to make sure that none of them are blown. If any of the fuses related to the AC or blower motor burn out then they can cause the system to not function. If the fuses are okay then it may be possible that the blower motor itself needs to be replaced. The reason the you may be getting air at higher speeds may be because at higher speeds there is airflow that the AC system can use. If the AC is set to allow fresh air into the vehicle, as opposed to cycle the same air, it may be allowing air through the vents when you are traveling at higher speeds. It may also be possible that there is an issue with the AC control unit. This is the component that contains the AC system's control switches, or even a wiring issue, perhaps related to the control unit or blower motor. I would recommend having a professional technician, such as one from YourMechanic, come to your location to (diagnose the cause of your AC system malfunctions)[https://www.yourmechanic.com/services/ac-is-not-working-inspection].

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