When I start my Jeep to let it warm up the heater blows hot air and it blows it like it should on high, but when I drive down the highway for about 20-30 miles and go to turn the fan up, it barely pushes any air out. I can hear it blowing under the passenger dashboard, but there is barely any air coming out of the vents. It doesn't have a problem heating. It only happens when I am driving down the highway for a ways. I have cleaned the in cab filter but haven't tried anything else. When I pull the filter out and turn the fan up it blows air out of the filter alot good, but when I put it back together it still won't push any air out of the vents, doesn't work on floor, front vents, defrost, and also doesn't work on recirculate.
My car has 45000 miles.
My car has an automatic transmission.
If your heater only blows when the setting is on high, this may suggest that you have a faulty blower motor resistor. The highest speed setting may still work because in most cars in the highest fan speed settings the current bypasses the blower motor resistor. In some cars, if the resistor is failed, the fan may stop working completely. Another reason a blower motor resistor may fail is when the blower motor has a mechanical problem or when a foreign object jams the blower motor fan blade and prevents it from spinning freely. This leads to increased current through the resistor and causes it to overheat and fail. I would suggest having an expert from YourMechanic come to your location to diagnose your system to determine what may be causing the fan not to work properly.
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