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Q: Heater blower surge

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My heater blower works at all speeds,but continues to jump from any fan speed to high momentarily,then back to the selected speed-just continues to surge like that,while driving or sitting still

My car has 170000 miles.
My car has an automatic transmission.

Hi There,

It sounds like you may have a faulty blower motor resistor. Blower motor resistors are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically, using a rotating lever, or electronically by the air conditioning system. The change in resistance then limits the current through the motor, which dictates the speed at which the blower fan works. Blower resistors, being a mechanical component, are prone to wear and are the most common point of failure in a car’s heating system. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.

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