Simply, the blower motor pushes air through the vents. And the speed of the blower motor is controlled by you via some switches, buttons and dial on the dashboard. There is a resistor inside the blower motor allowing you change the speed. Therefore, if the heater fans in your BMW car operate at only one speed rather than multiple speeds or the air is not coming out of the vents, there is a possibility that your blower motor is failing or worn. Since it is quite an easy job to replace the blower motor at home, so why don't you try it? All you need to do now is get a brand new and we offer you all BMW genuine OEM blower motor with an attractive low price.