Blower motor resistor
Ford blower motor resistor
A blower motor resistor is a part of a vehicle heating and ventilation system. It controls the speed of the blower motor. It's only used in cars where the blower motor speed has several fixed speeds, usually 4 or 5. The most common symptom of a failed blower motor resistor is when the heater fan only runs at high speed and doesn't work at low speeds. In some cars, a failed blower motor resistor can cause a heater fan to stop working completely.
Problems with a blower motor resistor are common in many cars.
How is the blower motor resistor diagnosed?
Often a visual inspection of the resistor reveals the problem. In many cases it's the result of corrosion, see this photo.
A failed resistor tested with an ohm-meter
If the resistor shows no visual damage, the resistance between terminals must be checked and compared to specifications. If the resistance is out of specs, the resistor must be replaced. For example, in this photo we measured the resistance of this blower motor resistor. According to the service manual, it must be around 4-5 ohms. In our case the ohmmeter shows open circuit, which means the resistor has failed. Often a blower motor resistor fails due to problems with the blower motor itself. We have seen instances where a worn-out blower motor causes a recently replaced resistor to fail again. For example, this issue was common in older Chrysler and Dodge minivans. In this case, the blower motor must also be replaced. The blower motor replacement costs from $320 to $650, depending on the car.
Where to take your car for repairs?
Your local meconic or any small repair shop should be able to diagnose the problem. Of course, the quickest way is to make an appointment with your local dealer. Many dealers have the part in stock. The blower motor resistor replacement is not very expensive. When the fan stopped working at lower speeds in our 2010 Ford Escape, it cost us $50 to diagnose and $112 to replace at our local Ford dealership. When the same problem occurred two years later, we ordered the part online for $25 and replaced it in our driveway. In 2008-2011 Ford Escape, the resistor is located behind the glove box on top of the ventilation duct. It's held by two screws and is easy to replace.
In the 2008-2011 Ford F150 the blower motor resistor is also located behind the glove box, but is installed in the right side of the plastic air duct. This thread at f150online.com shows where the resistor is located. The author of this blog shared his experience of replacing the blower motor resistor in Jeep Liberty. In some older cars and trucks the blower motor resistor is installed on the firewall, with the access from under the hood.
Where to buy a part?
If the part is too expensive at your dealership, you can order it online. We checked Amazon, eBay, RockAuto and AutoZone websites and found their prices much cheaper. For example, the blower motor resistor for the 2008 Ford Escape is sold for $16-$30 online, which is almost half the price we were quoted from our local Ford dealer parts department.