Q: Blower motor randomly works

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The blower motor is randomly working. While searching for a solution, I jiggled the wires under the dash and that seemed to help slightly. Even after the dealership replaced the motor, still had the same problem. It’s a 3-terminal motor and I’m assuming it has on-board transistor diode pair of PWM operation. Is it a N-channel or P-channel FET and would tying the transistor gate to one of the other pins turn the motor to full blast?

The blower speed is controlled by a final stage unit sometimes referred to as a blower resistor by an auto parts store. This is located on the passenger side of the heater box and has probably failed. A lot of times this unit can fail due a faulty blower motor that has been drawing a lot of current during its operation. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will have the tools and expertise to diagnose the blower circuit and correct the blower issue.

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