National average cost of a Blower Motor Resistor Replacement for popular vehicles:
What is a blower motor resistor and how does it work?
A blower motor resistor is an electrical component that is part of the heating, ventilation, and air conditioning (HVAC) system in your vehicle.
Housed in a special duct below your dashboard ahead of the glove box is a fan - the blower motor. The blower motor is responsible for introducing either warm or cool air into the passenger compartment when you turn on the heat or AC.
In order for you to be able to adjust the speed of the fan, a resistor is inserted into the electrical pathway leading to the blower motor. This blower motor resistor alters the amount of electrical current flowing to the fan motor in response to changes you make to the climate controls.
How do I know if my vehicle needs the blower motor resistor replaced?
Since the blower motor resistor responds to the climate control settings when you adjust them, a faulty resistor will show itself when those controls do not work as they should. If the resistor is bad, the fan might not blow air through the vents intermittently or not at all. The fan might work on one speed setting, but not on another. You might even find that the fan comes on only when your vehicle hits bumps in the road, jarring the bad resistor into intermittent action.
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To replace a blower motor resistor, a technician will take steps specific to your vehicle make and model. That is because access to the blower motor is different from one model to the next. In general, steps to blower motor resistor replacement include
Disconnect your vehicle’s battery, taking care to preserve the computer memory settings
Disassemble the lower dashboard to gain access to the blower motor and resistor
Disconnect the wiring harness connector to the resistor
Unfasten the resistor and remove it from the fan housing
Insert and secure the new resistor and plug it into the harness
Replace all of the dashboard parts removed for access
Reconnect the battery and verify that the repair was successful
Note that some blower motor resistors are located not inside the dashboard but in the engine compartment. In these cases, the process for replacing the resistor may be less involved.
OTHER QUESTIONS CUSTOMERS ASK
How do I know if I need to replace the blower motor or the blower motor resistor?
One way to tell that the blower motor resistor is faulty (rather than the blower motor itself) is when the fan runs on some speed settings but not on others. If the blower motor fails, it will usually fail to function at all, whereas a bad resistor is often intermittent or partially impaired.
What causes a blower motor resistor to fail?
Blower motor resistors fail for several reasons, including overheating, excessive current draw from the blower motor, or corrosion. To promote cooling, the blower motor resistor is often mounted in the stream of cool air entering the HVAC system from outside the vehicle. Unfortunately, this also means that the resistor is exposed to moisture, salt spray (during winter driving), dust, and other airborne contaminants drawn into the HVAC system. All of these contribute to corrosion of the resistor coils and possible overheating.
Why does the fan in my car only work on high?
The blower motor resistor changes the amount of electrical current that flows to the blower motor. “High” speed is the normal amount of current, and the lower speeds are due to designated degrees of electrical resistance. If the resistor fails, it is possible for the electrical signal to bypass the resistor in its normal “high” state. This results in a fan speed that only runs on high and is unresponsive to other settings.
What parts are related to a Blower Motor Resistor Replacement?