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We get a lot of questions about the resistor in the HVAC system. It seems redundant, but the blower motor can never move more air than it can on “Max.” So, to get different speeds out of the motor, it is slowed down with a resistor pack (arrow). The resistor pack heats up, so it is placed in the heater box in the flow of air to help cool it off. It can go bad without the blower motor also being bad. Typically, a failing resistor pack is evidenced by a loss of speeds.