The fan in a car’s heating and air conditioning system is driven by a blower motor. Corrosion or overheating can cause a blower motor resistor to fail. The blower motor resistor can occasionally become overheated and suffer early damage as a result of the mechanical resistance to the motor rotation.
It becomes more challenging or impossible to adjust the airflow speed when the resistor fails. The electrical circuits need to be examined in order to diagnose them. Numerous components that could result in the same issues are present, but they are all conveniently close to one another to facilitate diagnosis.
Today, you’ll get to know the definition, location, function, signs and symptoms, diagnosis, replacement cost, and how to replace the blower motor resistor. You’ll also be provided with answers to frequently asked questions about the blower motor resistor.
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Contents
What is the blower motor resistor?
A blower motor resistor is an electrical component that has the capacity to stop the passage of current into the blower fan motor. In other words, Blower resistors are resistors that are used to control the speed of blowers in automobiles.
The blower resistor resistance can be changed mechanically by rotating a lever, or electrically by the air conditioning system, to alter the fan speed. More resistance causes the fan to spin less quickly, which reduces the amount of hot or cold air that is circulated across the whole cabin.
The blower motor will likely receive the maximum current and operate at full speed if the resistor burns out or wears out due to corrosion because there is nothing to reduce the voltage going to it for the lowest fan speed.
No matter what fan speed is selected, the fan will tend to run only at higher speeds or at its highest speed when a resistor fails. However, the fan may not operate at all in some cars, and just a small amount of air may pass through the vents.
There may be a problem with the fan’s blower motor, a switch or resistor that adjusts fan speed, or there may not be enough air flowing through the vents (hot or cold).
Read more: Understanding the car Air conditioning condenser fan
Where to find the blower motor resistor
Under the dashboard is usually where you’ll find the heater blower motor resistor. It can be found in the compartment housing the heater and air conditioning.
It can change the blower motor fan’s speed because it is connected to the air conditioning system. Some automobiles also have it concealed under the glove box. In either case, you can locate it not far from the blower motor.
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Function of the blower motor resistor
The part that controls the blower motor’s speed is a blower motor resistor, also referred to as a blower motor control module. The resistor controls how fast the blower motor operates when the fan speed on your car’s instrument cluster is adjusted. The resistor undergoes significant wear as a result of the numerous fan speed adjustments.
It could fail at any point due to the ongoing stress. Depending on the fan speed selected or, in the case of an automatic climate control system, the interior temperature and other factors, the heater blower motor increases or decreases the amount of air blowing through the dashboard vents.
However, by limiting the amount of electrical current going to the blower motor, resistors—small, hidden electronic components—actually regulate the fan speed. Setting the fan speed to its minimum level, for instance, will signal the resistor to limit the amount of current to a low level when everything is operating as it should.
Signs and symptoms of a bad blower motor resistor
In many cars, blower motor resistor issues are common. When the heater fan only operates at the highest speed setting (4 or 5) and not at lower settings, this is the most common symptom that the blower motor resistor has failed. Failure of the blower motor resistor in some vehicles can result in the heater fan not operating at all.
Here are some signs you’ll notice when your car’s heater blower motor resistor is going bad:
- Only one speed from the blower motor
- Some airflow settings are not working
- No air is coming from the vents
Only one speed from the blower motor
A common symptom that your car’s blower motor resistor is faulty or going bad is when it becomes stuck in the on position. This means that you’re unable to adjust the speed. You could still use the heater or air conditioner, but you’ll need to fix it so that it works properly once again.
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However, in some cases, the speed may occasionally come on and go off. But to avoid this, you’ll need to replace the heater blower motor resistor. Other faulty HVAC parts can also contribute to this issue. To be sure they aren’t broken, you will need to examine the connections to the motor and fan switch.
Some airflow settings are not working
As a result of the heater blower motor resistor going bad, you may notice that not all the airflow settings are working. The resistor for the blower motor is not required while the system is off.
The resistor is essential for controlling the flow in the other settings. However, the blower motor switch may also be responsible for this issue. As a result, you might need a further test to identify the faulty part.
No air is coming from the vents
You might not be able to get any air to come out of the vents when the resistor fails. The blower motor resistor controls the power going to the blower motor in the system. It may shut off all power to the motor if it fails.
Air pressure cannot be produced if the blower motor is not powered. The only thing left is a heater or air conditioner with no air escaping the vents. If nothing is coming out of the vents, there are other things you would want to check before the resistor. If nothing is functioning, you ought to start by checking the fuses.
Read more: Understanding automobile air conditioning system
Diagnosing the blower motor resistor
Sometimes, a quick visual inspection reveals the issue. For instance, as you can see in this image, corrosion caused the blower motor resistor to fail, and by seeing this, we know there’s a need for replacement.
The resistance between the terminals must be inspected and compared with specifications if the resistor has no visible damage. The resistor needs to be changed if the resistance is not within specifications.
A blower motor resistor may occasionally fail as a result of issues with the blower motor itself. This indicates that after changing the blower motor resistor, ensure that the blower motor runs quietly and freely.
In some cases, an old blower motor will make a newly replaced resistor fail once again. When the blower motor makes a loud screeching noise when running, it’s one of the signs that the blower motor has worn out and must be replaced.
Replacement cost for the blower motor resistor
Depending on the type of car you drive, the cost to replace the heater blower motor resistor could range from $10 to $60. This is one of the most affordable replacement parts for heaters and air conditioning.
Depending on where you reside and the kind of car you drive, the usual labor prices to replace a blower motor resistor vary. It is advisable to compare quotes because you might receive a variety of them, some of which may cost nearly twice as much from another company.
For the replacement of a blower motor resistor, you should typically budget between $50 and $200 for labor, bringing your total to between $60 and $260 for parts and labor.
The blower motor resistor, however, can be easily and quickly fixed at home in about an hour (even if you’re a beginner) and for about $60 since you will be the one to replace it. There’s no labor cost applied.
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How to replace the blower motor resistor
You often need to replace both the blower resistor and the fan since a bad heater fan can often cause the heater blower motor resistor to fail. Additionally, replacing it is not difficult.
The diagnosing process could take longer than simply changing the resistor. If you’re not confident doing it yourself, you’ll need to hire a qualified mechanic to carry out the job.
Here are some steps to take to replace the heater blower motor resistor:
If necessary, take off the glove box door
Normally, you can simply push in on the sides and lower the door away from the dashboard to remove the glove compartment. Some vehicles might need special tools to remove this component, while others won’t even let you open the glove box to access the blower motor resistor.
Disconnect the wiring harness and unscrew the screws
Sometimes it is easier to take the harness off first, depending on where the blower motor resistor is. It is easier to take the resistor out of the housing on some vehicles before disconnecting the harness.
Remove the faulty one and replace it with the new blower motor resistor
The blower motor resistor simply slides out of the HVAC housing after the screws have been removed and the wiring harness has been disconnected.
Make sure to remove the old gasket as well if the new resistor has a rubber or foam gasket material around the outside edge. Some resistors may not have any kind of gasket at all.
You can test the appropriate working of just a new blower motor resistor before completing the whole installation by loosely installing the new resistor and making sure that all of the blower motor fan speeds function as intended.
Tighten screws and reconnect the wiring harness
Then, tighten the screws and reattach the wiring harness in the same way that you removed it the first time after making sure the blower motor is operating properly.
Reinstall the glove box door
Reinstalling the glove box, if it had to be taken out in order to reach the blower motor resistor, will be the last part of this do-it-yourself fix.
FAQs
How do I know if my blower motor resistor is bad?
Loss of HVAC fan control (total or certain speeds) The fan only operates at its maximum speed. Vents aren’t blowing any air. uneven or irregular fan speed
What happens when the blower motor resistor goes out?
The blower motor resistor is what supplies power to the blower motor, so if it breaks down or develops any problems, power can be cut off to the motor. Without power, a blower motor will be unable to produce any air pressure, leaving the HVAC system without the ability to produce airflow through the vents.
How much does it cost to replace a blower resistor?
Depending on the type of car you drive, the cost to replace the heater blower motor resistor could range from $10 to $60. This is one of the most affordable replacement parts for heaters and air conditioning. For the replacement of a blower motor resistor, you should typically budget between $50 and $200 for labor, bringing your total to between $60 and $260 for parts and labor.
Where is the blower motor resistor?
The blower motor resistor is typically quite simple to access; however, positioning your body inside the vehicle to remove the component can be challenging. The resistor is either near the glove compartment or at the bottom of the HVAC housing.
Will a blower motor work without the resistor?
In some cases, a faulty resistor will completely stop the current from flowing to the blower motor. The motor won’t operate in the absence of power. The blower fan remains stationary and silent as a result, and no air is blown out from the vents.
What causes a blower motor resistor to go out?
The blower fan resistor typically fails as a result of corrosion or overheating. Your car won’t blow any forced air if the blower fan fails. However, occasionally the blower motor itself may be the issue. This is particularly obvious if the blower fan has been replaced several times.
How long do blower resistors last?
The blower motor resistor is intended to last for the lifetime of a vehicle. Most of the time, these resistors will break before the car. The continual use and heat exposure that the blower motor resistor experiences are typically what cause it to wear out.
How long does it take to replace a blower motor resistor?
Depending on the experience you have with replacing the blower motor resistor, it will take you a different amount of time. However, if it’s behind the glove box and the glove box is simple to remove, it can take up to 15 minutes!
Does the blower motor affect the AC?
Your air conditioner’s blower motor is a crucial part. The level of comfort and air quality in your cabin can be strongly impacted if it isn’t functioning properly.
How do you know if a blower is bad?
- Only one speed from the blower motor
- Some airflow settings are not working
- No air is coming from the vents
That is all for this article, where we discussed definition, location, function, signs and symptoms, diagnosis, replacement cost, and how to replace the blower motor resistor. We also discussed the answers to frequently asked questions about the blower motor resistor.
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