Blower Resistor (Fan Speed Resistor)
The blower resistor sets the heater fan speed by adding resistance in the motor circuit; newer cars use an electronic power module for the same job.
What is Blower Resistor (Fan Speed Resistor)?
A classic resistor pack has several coils, and each fan position routes the current through a different amount of resistance. The highest speed often bypasses the resistor completely, which is why a failed resistor typically leaves only the top speed working. Climate-control cars usually have a transistor-based module that is controlled by a PWM or voltage signal from the climate unit.
How it works
Extra resistance reduces the voltage reaching the motor, so it turns more slowly; the heat produced is carried away by the airflow.
Why it matters for your car
A seized or worn blower motor draws more current and is a common reason why resistors burn out repeatedly. Melted connectors at the resistor are a sign of high current or poor contact and should be repaired together with the part.
Other terms
- Brake Bleeding
- Electronic Brakeforce Distribution (EBD)
- Gear Whine
- Kingpin
- Monocoque (Unibody)
- Nitrogen Tyre Inflation
- Oil Consumption
- Part-Worn Tyre
- Permitted Axle Load
- Piston Slap
- Power Steering Pump
- Range Extender
- Rear Quarter Panel (Rear Wing)
- Seat Adjustment
- Snow Chains (Tyre Chains)
- Spare Wheel
- Top Tether Anchor
- Underbody Protection
- Wheel Runout
- Wireless EV Charging (Inductive Charging)