Q: My high speed on my blower not working new resistor motor is good what could it be the relay

asked by on

no high speed
My car has an automatic transmission.

Hi There, The resistor is what controls the speed of the blower motor, not the relay. The blower motor relay supplies power to this motor when you turn the switch to "on" that can sometimes fail. When this happens, you may notice that you will not feel anything blowing out of the vents at all. This may also cause the blower motor to work intermittently. A blower fan is connected to the negative battery terminal (also called ground) on one end and to the positive battery terminal through a blower motor resistor on the other end. The blower resistor is connected in series to the blower fan motor. This means that the current running through the blower motor, and its’ speed is therefore controlled by the resistor value. The user chooses a fan speed by selecting a speed which then connects one of the resistors in the blower resistor pack. Blower resistors are made of several resistors with different resistances. There are also two additional circuits used for the off state of operation as well as the highest speed of operation. In the off state, the blower motor is effectively disconnected from the power supply. In the highest fan speed state, the blower resistor is bypassed completely and the fan is effectively connected directly to the car’s battery, allowing maximum current to be supplied to the blower motor. The lower the resistance of the selected resistor in the pack, the higher the current that flows through the blower fan causing the fan to turn faster.

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