An A/C blower motor resistor is an electrical device that controls the speed of the blower motor in a vehicle’s heating, ventilation, and air conditioning (HVAC) system. It does this by varying the amount of electrical current that is sent to the motor.
When you turn the blower motor knob to a higher setting, the resistor increases the resistance to the current flow, which reduces the amount of power that is sent to the motor. This causes the motor to spin slower, resulting in a lower airflow.
When you turn the blower motor knob to a lower setting, the resistor decreases the resistance to the current flow, which increases the amount of power that is sent to the motor. This causes the motor to spin faster, resulting in a higher airflow.
A/C blower motor resistors are typically located under the dashboard or behind the glove box. They are relatively inexpensive and easy to replace, but they can fail over time.
Here are some of the symptoms of a bad A/C blower motor resistor:
- Intermittent blower motor operation
- Blower motor that runs at full speed or full low speed only
- Blower motor that makes a humming or buzzing noise
- No blower motor operation at all