What are the symptoms of a faulty car air conditioner blower resistor?

[McJanelle]

The main function of the car blower resistor is to control the speed of the airflow. If it is damaged, the most obvious symptom is the inability to adjust the air conditioner's fan speed. The method to diagnose it is also simple. Prepare a multimeter, set it to the ohm scale, place the red probe on the positive terminal of the resistor and the black probe on the negative terminal. Then check if the reading on the multimeter is normal. If the measured resistance value is 0, it indicates that the resistor is faulty. The steps to replace the blower resistor are as follows: Prepare the replacement blower resistor, a Phillips screwdriver, and other tools, then turn off all electrical devices and the ignition switch of the car; disconnect the car battery and the blower assembly connector (the blower is usually located under the glove compartment on the passenger side), remove the blower's fixed wiring harness, and then unscrew the blower assembly's mounting screws; You can find the resistor at the location where the blower is removed (connected near the air duct), use tools to remove it, and install the new resistor; Reinstall the blower and all wiring, reconnect the battery, start the car, and activate the blower to check if the fan speed can be adjusted. It is best to go to a 4S shop or a professional repair shop to replace the blower resistor. Because the replacement process involves wiring issues in the car's electrical system, improper operation may damage the blower or even burn out the car's circuits.