Last Updated on October 22, 2023 by Kevin Chen
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A blower motor resistor is an integral part of your vehicle’s heating and air conditioning system. A blower motor is responsible for determining the speed at which the fan rotates. All this happens due to the behavior of the resistor as it influences the rotation speed of the blower motor, onto which a fan is attached.
In as much as blower motor resistors are reliable, they can suffer physical and electrical damage. Cases of overheating and corrosion are likely to affect the state of the resistor. And once this happens, you will have to do a replacement.
Before you proceed to replace your blower motor resistor, it will be smart to know the basics and even the technical aspects of it. Keep reading as we break down everything you should know about the blower motor resistor.
Defining a blower motor resistor
Probably you know what a resistor is. This is an electronic component designed to limit the normal flow of electric current. In our case, the resistor stops the flow of current toward the blower motor.
Keep in mind that the flow of current has a direct impact on the speed of the blower fan. So, we can confidently state that the blower motor controls the speed of blowers in vehicles.
A blower motor resistor is just like other normal resistors only that it has the capacity to handle a significant amount of electric current. Also, it is designed to have multiple resistance values making it possible to rotate at different speeds depending on the heating or cooling requirements of the vehicle.
Where is the blower motor resistor in a vehicle?
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In most vehicles, the blower motor resistor is located right under the dashboard. In some vehicles, the blower resistor is concealed beneath the glove box.
Typically, you will find it along the vehicle’s HVAC meaning that it should be right next to the blower motor.
A wiring harness connects the resistor to the control module. It is at the control module that you will be able to change the value of resistance on the blower motor.
How does a blower motor resistor work?
The working principle of a blower motor resistor is similar to that of other resistors.
First, it all starts with the HVAC module receiving input from the driver or passenger. The input will depend on the desires of the person, it may be to increase the speed of the fan or to slow it down.
The control module will then send the signals from the driver or passenger to the blower motor resistor. The relayed signal will depend on the desired speed of the fan that you want.
The blower motor resistor will receive the signals and respond accordingly. The resistor will control the amount of electric current flowing to the blower fan depending on the selected speed.
Would you like the fan to rotate at a high speed, the resistor will allow sufficient current to flow. The reverse is true if you would like the fan to be slower.
In most HVAC systems, there are multiple motor resistors with different resistance values. Each resistor responds to different speed requirements. As you change the speed gradually, the resistor will switch from one to another. Such a connection has smart signal management that is able to control the switching actions of the resistors.
When several resistors are used in a single HVAC unit, failure by one resistor will force the fan to operate at a single speed.
Whether it is a single resistor or multiple resistors, its resistance value must match the supply current for an efficient operation.
Possible causes of a damaged blower motor resistor
There are several factors that can make the blower motor resistor stop working. Here are the most probable cause of damaged resistors.
- Overuse: Blower motor resistors are not built to last forever. Time can catch up with them and they will stop working as usual. A blower motor resistor that has been in operation for a long will start underperforming and finally, cease operating. So, if you have been using the resistor for a long, you should consider replacing it.
- Wrong voltage: Overvoltage in the vehicle will affect different electrical components, including the blower motor resistor.
- Electrical mishaps: Numerous electrical issues can affect the overall functioning of the vehicle’s HVAC and resistor. These issues include bad wiring and even short circuit.
- Physical damage: A blower resistor may be exposed to various physical conditions that can lead to wear, tear, and even breakage. A physically mutilated resistor will definitely fail to perform effectively as it should.
- Low-quality resistor: The problem could be with the resistor. Low-quality resistors are prone to constant damage. Ensure you get the best quality blower motor resistors from reputable electronic components suppliersand distributors in China.
- Improper installation: What if you just didn’t install the resistor well as it is supposed to be? This can also cause some serious damage
Signs of a bad blower motor resistor
Now that you know the causes of a faulty resistor, here are the key signs that your motor resistor is not functional:
- Single speed: Does your fan rotate at one speed only? If it cant go any faster or slower than a particular speed, chances are it is damaged.
- Inconsistent airflow: This happens when the air coming through the vent is not constant or even predictable. For example, there will be more air coming through when it is supposed to be low
- The blower motor not working: Well, what if the blower motor refuses to rotate at all? The resistor may be damaged.
- Burnt smell: A burnt smell emanating from the vehicle’s HVAC system could be due to the overheated resistor.
Once you notice and even experience any of these signs, it will be advisable to have a professional automotive electrician check the vehicle. In most cases, a replacement will be the ultimate solution.
When replacing the blower motor resistor, ensure that its resistance values match the HVAC system requirement. It should also be of premium quality and bought from a reputable suppliers.
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