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Blower Motor Guide in 2024

blower motor guide

Vehicle air conditioning systems provide heated or cooled air, but not without the help of a component called blower motor. The AC blower motor, as it is also called, spins to force air through the dashboard vents and into the cabin. Whether searching for help to shop for the blower or looking to understand how it works, you’re in the right place. This article is a thorough guide into what blower motors do and how to go about buying for one.

The car blower motor is not a common part. Many people do not know its function or even where to find it in a vehicle. So we will start there.

A complete Guide to the Automotive Blower Motor

Blower Motor Definition and Location

The blower motor is the electric device that pushes heated or cooled air into the cabin. It forms part of a vehicle’s HVAC system. When switched on, the blower ensures a constant supply of conditioned air via the vents on the dashboard. The blower is usually a motor and fan assembly fitted with electrical connections.

The blower motor wiring system includes several components such as fuses, resistor module and, at times, a relay. Most blowers mount under the dashboard and on the passenger side. Some vehicles have the component installed in the engine compartment, on the fender.

A majority of cars use one blower for the HVAC system. Some large vehicles such as vans and SUVs have two; one in the front and another in the rear. Blower motor features and configurations vary slightly. However, some major parts are identical as explained next.

blower motor diagram and entire HVAC system

Parts of a Blower Motor Assembly

The car HVAC blower motor is only made up of a few components. These must work together for the assembly to be functional. If one of them fails, you have a bad blower. Some are replaceable, though, and do not require replacing the entire unit if damaged. Main blower motor parts include the following.

DC Motor

The blower uses a small but powerful motor as the engine of the assembly. The motor is usually either the brushed or brushless. Brushed motors are a traditional design and mostly found in the blower assemblies of older cars. Many lately manufactured vehicles come equipped brushless blower motors.

A blower motor that does not use brushes has many advantages. It has fewer rotating parts and, therefore, fewer components that are prone to wear. It also does not produce sparks when in operation, which makes it more efficient and durable.

The ability for infinite speed control with brushless blower motors is another attribute that makes them better than the brush types. You also do not need a resistor module to control their speed, as that can be done electronically.

Blower Motor Wheel/Fan

The blower motor fan is also called a wheel or cage due to its design. It comprises plastic blades that are arranged to channel or direct air when rotating. That enables the blower motor to ensure sufficient hot or conditioned air inside a car cabin.

The speed at which the wheel rotates determines the amount of air moved. That, in turn, controls the cabin climate and contributes to the level of comfort for the driver and passenger. In older cars, the blower speed is controlled by a resistor module.

Newer cars have the speed controlled by an electronic component called blower motor control module. The module contains clever electronics to vary the voltage supplied to the motor. The module offers a more efficient way to vary the motor speed. It also allows the blower to be run at very low speeds.

Blower Motor Housing

The housing is the blower motor cover that keeps out debris and other material that may damage the motor. The housing also provides the mounting surface to attach the assembly. The electrical harness or connectors that supply current to the motor also mount on the housing.

Other major components associated with the device are fuses, relay, and resistor. The blower motor relay switches power to the motor using a low current signal, while the resistor allows for speed variation. The blower motor resistor is only found in older models of the device or those that use brush-type motors. In newer models, an electronic module performs the resistor’s role.

blower motor working

How a Blower Motor Works

The blow motor helps to pump cooled or heated air into the vehicle cabin. Without it, the HVAC system working would not produce noticeable results. Most parts of the cabin would remain cold in winter or hot in hot weather. The blower, as we have seen, consists of a simple construction involving a DC motor and special wheel fan composed of plastic blades

When voltage is applied, the motor starts to spin, thereby rotating the fan assembly or wheel. The fan pushes air through HVAC system’s heater core to heat the cabin. To cool the cabin, it channels air to the AC evaporator. The amount of air moved depends on the speed of the motor.

Blower motor speed control methods vary depending on whether you have a brush or brushless motor. Brushed motors rely on a resistor to change the speed, brushless motors an electronic circuit called a control module. The function of the two components is explained below.

Blower Motor Control Module/Resistor Function

In most brush-type motors, the speed controls are physical dials or levers. These work together with a resistor module. The module contains resistors of different Ohm values. Each resistor then offers a specific blower speed by limiting the amount of current that goes to the motor.

There are also the two extra settings on the controls, one for the “off” and another maximum blower speed. The “off” setting cuts off current completely, stopping the blower from running. The maximum speed setting bypasses the resistor module, allowing the motor to receive maximum voltage and spin the fastest.

Brushless blower motors use electronic speed control. The system consists of transistors and a circuit board to communicate with the motor. One of the advantages of the blower motor module is that it allows the use of sensors. That, in turn, makes automating speed control possible. Most modern cars come equipped with these types of controls for the blower.

Both the electronic and resistor control systems allow different levels or air heating or cooling. However, the resistor model is more prone to overheating than the electronic types. As a result, they are normally mounted in one of the HVACs ducts. The air in the duct then

checking a blower moor for damage

Blower Motor Problems

Blower motors rarely operate under stress unless debris gets lodged in the fan blades. They are, therefore, more likely to last a long time. Besides normal wear and tear, other situations that may cause problems include mechanical impact, corrosion, and shorting. Here is a look at the issues you are likely to experience with the component.

Electrical faults

These include a burnt or corroded resistor module and connections, bad relay, and burnt motor or fuse. Damaged resistors cause the blower to lose speed control. If completely burnt out or corroded, you may only have access to the highest fan speed. The blower motor speed control module could also fail and cause problems.

Loose connectors could cause the motor to turn on intermittently, while corroded leads affect the delivery of current to the motor. Bad relay or burnt motor and fuse result in a blower that stops working. You can replace a relay or fuse. The electronic or resistor module too. Cleaning corroded leads and re-installing loose connections should restore the motor operation.

Mechanical issues

These include clogged moving parts and broken fan blades. Despite the blower motor location, debris can still reach the rotating parts and cause obstruction. When that happens, using the blower puts a strain on the motor and reduces its lifespan. It may even cause the blower to stop working.

Large debris lodged in the fan blades could cause them to break. Although that may not affect rotation, the fan may not be as efficient as before. Cleaning a clogged blower motor assembly is all that’s needed to correct clogging problems. If the blades are broken, replacing the entire blower would be the only solution.

Mechanical damage inside the motor itself includes bad bearings and worn brushes for the brush type motors. Well maintained motor bearings ensure the correct fan rotation. If broken, the resulting wobble would affect the assembly’s efficiency or cause the motor to get stuck. Worn brushes may cause the blower to stop working.

To identify blower motor problems, mechanics usually test all the components involved in its working. These include relays, fuses, resistor modules, electrical connections and the motor itself. The tests help to isolate faulty from non-faulty components. Besides the blower motor test, a physical examination of the assembly can help to identify problems.

new blower motor assembly

Motor Blower FAQs

Q1. What does a blower motor resistor do?

A. The resistor controls the fan speed, often using mechanical controls to vary the resistance. It’s usually a module consisting of several resistors with varying resistance values. By selecting a specific resistor, the person adjusting the HVAC system raises or lowers the speed at which the fan rotates. A blower motor resistor normally connects on the positive side of the battery.

Q2. Can you replace a blower motor resistor?

A. You can. The resistor is one of the replaceable parts of a blower. It’s also one of those that get damaged too soon. The resistor often fails due to overheating. Corrosion is also another reason for a failed resistor although not often. Luckily, you can easily tell when that happens. Signs include the blower losing speed settings, only having a high speed setting or only low. Blower resistors are normally sold as single pieces.

Q3. What is the blower motor repair cost?

A. The cost to replace a blower resistor depends on the type and make of your vehicle. Prices range from as low as $10 to as high as $200 or more. Adding labor charges, the amount ranges from $70 to $150 for most cases and considering the cost range of most resistors. The task itself lasts around an hour or less, although it depends on the experience of the specific technician.

Q4. Where is the blower motor fuse located?

A. Blower motors often use two fuses. One fuse is located in the fuse box among those of other components. The other fuse is located in the engine compartment. Either fuse can blow at any time. They are among the reasons for the blower motor not working. They are easy to replace, though, even without the help of a mechanic. If a blower motor fuse keeps blowing, check the wiring for faults.

Q5. How long does a blower motor for car or truck HVAC systems last?

A. The blower is supposed to last the entire lifetime of your car. However, situations vary and some climates require the fan to be used too often. Many car owners find themselves having to replace the blower after five years. The quality of the motor used to power the blower matters. If inferior, you can expect to have a failed blower too soon.

Q6. How do you know that a blower motor is going bad?

A. Blower motors develop problems when the motor burns or wears excessively and does not function well. Also, if the relay is loose or damaged and affecting the electrical connection that supplies power to the motor. If the fuse is blown or wire connections damaged, the motor will not work. Other reasons include a broken blower motor wheel or what’s called the fan.

Common bad blower motor symptoms include the following

  • Weak airflow for both the heating and cooled air coming out of the vent
  • No air pushing through the vents (motor broken down or bad control module)
  • Unusual blower noise such as a rattle or squeak (worn motor or bad bearings)
  • Blower motor only works on high speed (damaged resistor)
  • Blower motor only work on low speed (faulty resistor or bad control module)

Q7. What causes a blower motor and fan to keep on running without stopping?

A. If the blower motor stays on when it shouldn’t, the reason could be electrical. You most likely have a failed control module. The module works electronically, and its diagnosis requires an expert. A mechanic can help establish the problem and advise what to do. If you have the knowledge and tools, you could test the blower and its wiring yourself.

Q8. Can a failing blower motor be repaired?

A. Some blower motor parts and associated components are replaceable. Examples include the resistor or control module, wheel, fuse, and relay. The parts do not require expertise to replace and only take a few minutes to install. If debris is clogging the assembly, cleaning it helps to free up the moving parts. Bad connectors can also be fixed. If the blower has served you for years, the best option is to replace it.

Q9. How much is the blower motor replacement cost?

A. The blower motor price varies between $300 and $500. Add the cost to install the component, which ranges from $50 to $100. The total cost for blower motor replacement could, therefore, be as low as $350 to as high as $600. Some car owners replace the device themselves. The task is fairly simple, especially if you are conversant with vehicle parts. If no it, it’s safer and more convenient to have it replaced by a mechanic.

Q10. How do you choose an AC blower motor for your vehicle?

A. The first step is to ensure you get a blower motor that is compatible with your type of car. That means using your car information to search for the perfect fit and avoid compatibility problems. Blower motors at build to be used in specific types of vehicles based on the year of make and the model.

What if considering a blower motor upgrade to cope with demanding climates? It’s possible to change your current blower to a better model, usually an aftermarket type. If that’s the case, consider looking for help from an expert such a mechanic. You don’t want to end up with the wrong kind of blower.

Other considerations include the price and brand reputation. Some blowers are costly, and you may want to look around for the best deals. If shopping online, a little more research can help you compare prices and identify the right brands.


The AC blower motor plays a significant part in keeping the air heating and cooling system functional. Unfortunately, many people overlook it until it fails and the car cabin becomes unbearably cold or hot. To ensure a functional blower motor always, it’s necessary to understand how it works and the signs of failure. That way, you can take early action and fix what can be repaired. You will also know when you need a new blower and how to buy the right one for your car or truck.

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