- Faulty blower motor resistor. The blower motor resistor controls the speed of the blower motor by varying the resistance in the circuit. If the resistor fails, the motor will only be able to operate on low speed.
- Worn-out blower motor brushes. The blower motor brushes make contact with the commutator on the motor shaft. Over time, these brushes can wear down and make poor contact, which can lead to the motor only operating on low speed.
- Damaged blower motor wiring. The wiring to the blower motor can become damaged or loose, which can prevent the motor from receiving power. This can cause the motor to only operate on low speed or not at all.
- Faulty blower motor switch. The blower motor switch controls the power supply to the blower motor. If the switch fails, it can prevent the motor from operating on any speed.
- Blockages: Check for any blockages in the air intake or outlet of the blower motor, as these can restrict airflow and prevent the motor from working properly.
Before attempting any repairs, turn off the power supply to the blower motor and consult the user manual for your specific HVAC system. If the problem is not easily identified, it is recommended to seek the assistance of a professional HVAC technician.
