With a faulty blower motor resistor, this problem is possible at any time. One of the worst possibilities is when the air stops blowing out of the vents. Therefore, a proper diagnosis is needed before you replace any parts. However, other problems can cause the same trouble, such as a defective blower motor switch. As an example, you may be able to use the lower fan speed settings but not the higher ones or vice versa. When the internal components fail or a short occurs, you are going to notice these malfunctions when attempting to change the settings. If you attempt to change the airflow settings and some don’t work, the blower motor resistor could be causing trouble.

You may still be able to get the heat or air you want, but you won’t be able to adjust the speed. So, when it fails or shorts, the motor can become stuck. The blower motor resistor is in charge of controlling the speed that the blower motor fan operates at. If you can’t get the motor off of a high or low setting, the resistor could be the problem. Yet, one of the most common symptoms of a defective blower motor resistor is when the motor gets stuck on one setting. You should be able to easily choose the setting you want the fan on. Most of today’s heater and air conditioning systems come with multiple fan speed settings.

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