What Does A Fan Speed Resistor Do

If the resistor isnt working properly then youll experience concerning and inconvenient symptoms in your bmws cabin. A failed blower motor resistor can cause issues with the operation of the entire heating and air conditioning system.

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Blower Motor Resistor Symptoms Testing

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In some cars a failed blower motor resistor can cause a heater fan to stop working completely.

What does a fan speed resistor do. A blower motor resistor typically located beneath the passenger side dashboard contains three resistors or sets of terminals designed to generate voltage in proportion to electrical current. These resistors allow the blower motor to function at lower speeds. As the fan speed is one of the most frequently adjusted settings of the air conditioning system the blower motor resistor is put under constant stress which can cause it to eventually fail.

As the fan speed is one of the most frequently adjusted settings of the air conditioning system the blower motor resistor is put under constant stress which can cause it to eventually fail. The most common symptom of a failed blower motor resistor is when the heater fan only runs at the highest speed setting 4 or 5 and doesnt work at low speeds. The blower motor resistor controls the speed of the blower motor indirectly by relaying electrical current to the blower motor control module.

Blower not moving any air. The system requires a motor called the blower motor which powers the fan utilized to propel air from your cabin vents. The cooling fan resistor is an electrical resistor that limits power to the fan in steps so that the fan can operate at different speeds according to the cooling systems demands.

The fan speed can be changed either by switching the blower resistor resistance mechanically using a rotating lever or electronically by the air conditioning system. The change in resistance then limits the current through the motor which dictates the speed at which the blower fan works. Since power to the cooling fan is sometimes routed through the cooling fan resistor when it fails or has any problems it can cause issues with the regular operation of the fans which can lead to overheating.

The blower motor resistor changes the speed of the fan but the switch on your dash board tells the resistor what resistance to select. In most cases a blower motor resistor fails due to corrosion or overheating.