A: Hello. If the blower motor resistor is experiencing repeated failure, the blower motor is likely drawing too much current. Excess current draw from the blower motor will cause the resistor to burn out.
The blower motor in your truck has a resistor block with multiple resistor wires. Each wire changes the resistance in the ground side of the blower circuit to change the speed of the motor. When the blower is turned to the high setting, the block is bypassed, allowing the blower motor a direct path to ground. That’s why your blower will only work on high when the resistor has failed.
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