The primary function of a car's blower motor resistor is to control the speed of the airflow. If it's damaged, the most evident symptom would be the inability to adjust the speed of the air conditioning. A straightforward way to determine this is by using a multimeter. Set the multimeter to the resistance (Ohm) setting, and place the red probe on the positive end and the black probe on the negative end of the resistor. Check the reading on the multimeter. If the resistance value reads 0, it indicates that the resistor is damaged.
Blower Motor Resistor Replacement Tutorial:
1：Prepare the replacement blower motor resistor, a crosshead screwdriver, and other required tools. Then, turn off all electrical devices in the car and the ignition switch.
2：Disconnect the car battery and detach the blower motor assembly connector (usually located beneath the glove compartment in front of the passenger seat). Remove the blower motor's retaining harness, then unscrew the mounting screws of the blower motor assembly.
3：At the location from which you removed the blower motor, you'll find the resistor (typically connected near the air duct). Use tools to detach it and replace it with the new resistor.
4：Reinstall the blower motor and all the wiring. Reconnect the battery, start the car, and turn on the blower motor to check if you can adjust the airflow speed.
It's worth mentioning that we don't highly recommend car owners replace the blower motor resistor on their own. The replacement process involves car circuit wiring, and if done incorrectly, it may damage the blower motor. In severe cases, it could even burn the car's circuits.
It's better to have it replaced at a reputable repair shop. The replacement cost is generally not very high, often just a few tens of dollars. Compared to doing it yourself and sourcing the appropriate resistor, going to a repair shop is more time-efficient and hassle-free.
