Blower Motor Fan Malfunctioning?
Check the Resistor Before Replacing the Blower Motor
One of the most common causes for perceived blower motor failure is a faulty blower motor resistor. The blower motor resistor varies electrical output to the blower motor to meet the selected fan speed settings.
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The blower motor resistor system in early model vehicles operated similar to a light bulb, a small wire with high electrical resistance to vary fan speed. Two wires were designated for low and medium speeds. It was common for the wire in this type of system to overheat and fail.
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Blower motor resistors in most of today’s systems can vary an electrical voltage up to 12V. They are commonly designed with an electrical circuit board. The most basic circuit boards allow for a select number of speeds, usually 3-4. Some advanced circuit board systems allow for a much wider range of fan speeds.
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If the fan speed for the A/C or heating system is not at the desired settings or only operating on one speed, it is most likely caused by a faulty resistor. In most cases, both the blower motor and resistor should be replaced at the same time.
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| 168_-_blower_motor_resistor.pdf |
