Why Do They Fail?

• Overheating caused by blocked cabin filters or restricted airflow.
• Age-related component wear affecting resistive elements or electronic circuitry.
• Electrical overloads placing excessive stress on the resistor or controller.
• Water ingress leading to short circuits and internal damage.
• Faulty blower motors drawing excessive current and overloading the control unit.
• Corroded or damaged connectors causing increased resistance and heat build-up.

Symptoms of a Failing Blower Resistor or Speed Controller

• Only one fan speed operates, often the highest setting only.
• No blower operation despite the motor being functional.
• Intermittent or erratic fan speeds that cut in and out.
• Blower runs continuously, even with the ignition switched off.
• Burning smell or visible heat damage around the resistor or controller.
• Repeated blower fuse failure caused by excessive current draw.

Fitting Tips

1. Always replace the cabin filter – blocked filters can restrict airflow and cause resistor overheating.
2. Test blower motor current draw – an overworked motor can damage a new resistor or controller.
3. Inspect electrical connectors for signs of corrosion, overheating or loose connections.
4. Confirm the correct replacement part – many modern vehicles use electronic blower controllers rather than traditional resistors.
5. Clear any HVAC fault codes after installation, particularly on vehicles with automatic climate control.