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How to Test A Blower Motor Resistor? 

How to Test A Blower Motor Resistor 

If you're looking for how to test a blower motor resistor, you first need to locate the resistor, test resistor fuse, tested the blower motor itself, and test the ground using a 12 Volt test light. 

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The blower motor resistor is one of the most important practical components in any heating or air conditioning system. Its main job Is to control the fan's speed which adjusts the blower motor speed. 

Since fan speed is the most adjusted setting in any air conditioning system, a lot of stress is put on the blower motor resistor, making it more susceptible to damages than any other component in your air conditioning or heating system. 

Over time of use, the blower motor resistor can get damaged, requiring installing a new component. A damaged or faulty blower motor resistor can affect the behavior of the air conditioning and heating system, which can be extremely frustrating for people living in very hot or cold environments.

This article provides you with all details you need to understand regarding the blower motor resistor. It will provide you with a basic description of the resistor's primary job, the main symptoms of a bad blower motor resistor, and a detailed step-by-step on how to diagnose the blower motor resistor yourself. Finally, it answers some questions any driver needs to be aware of when it comes to blower motor resistor replacement.

What is the blower motor resistor? 

The blower motor resistor is responsible for controlling the fan speed. Most blower resistors work either using mechanical, rotational, or electrical power.

Once you change the resistors limit, the sand speed is adjusted accordingly. Since the blower motor resistors work mechanically, they are the quickest component to fail any vehicle's heating system. 

How to test a blower motor resistor? 

The good news is that with the blower motor resistor certain troubleshooting yourself, the problem is coming from the blower motor resistor, not from something else.

Here's what you need to do to test a blower motor resistor:

  • Locate the blower motor resistors fuse 

The first thing you need to do is determine where the blower motor resistor fuse is located in your vehicle. To do so, you can either refer to your vehicle's owner’s manual or watch some YouTube videos or search through Google about where this fuse is located in your vehicle.

If you don't have a copy of the manual, you can always download it from the Internet or request a hard copy from your professional mechanic.

  • Test the blower motor resistor fuse

Once the blower motor resistor fuse is located, the next step is to test if it's working properly. To do so, use a 12 Volt test light and connect it from one side to the ground and the other side to the fuse terminal.

Monitor the behavior of the power on the terminals and see if the fuse is working properly. Both terminals should have power indicating that the fuse is working just fine. However, if they don't have power, the fuses burnt and require replacement.

  • Take out the blower motor resistor and test it 

Following the same steps mentioned earlier, make sure to unplug the blower motor and connected it to the 12 Volt test light. It's important to do the Test this way to prevent any confusion coming from components within the electrical climate control system in your vehicle.

When you perform the task, it is important to adjust the blower motor to different speeds to determine if there is any problem at certain speeds. If the blower motor is not working properly, you'll notice that it loses power at certain speeds. 

Keep in mind that if you set the blower motor to higher speeds and realize that there is no power, the problem can also be linked to a bad switch because, at certain high speeds, the blower motor receives the power from the switch. 

If you realize that the blower motor works just fine at higher speeds but not at lower speeds, then your problem is linked to the blower motor resistor itself. 

  • Test the blower motor ground 

Blower Motors rely on certain grounds connected to the vehicle's body, and sometimes a bad blower motor can happen due to a problem with the ground itself.

Rounds can wear out over time resulting in the intermittent function of your blower motor. Thus, if none of the mentioned tests indicated an issue with the blower motor resistor, you need to look at the blower motor ground because it might be the faulty component. 

What are the common symptoms of a bad blower motor resistor? 

When you adjust the air conditioning speed, you're basically adjusting the amount of electrical current passing through the blower resistor motor.

When the blower resistor motor does not work properly, you will notice one of the following symptoms

  • Systems allow very weak airflow 

When the blower motor resistor goes bad, you'll notice that the airflow coming from the vents is not going to be strong enough. 

Thus, if you notice that once you turn on the air conditioning or the heating system and the air is not as strong as before, you need to check the air blower motor as it might be the main culprit for the problem.

The air blower motor might wear out or get weaker over time reviews, preventing it from allowing the right amount of air to flow from the vents. This is a clear sign that the blower motor resistor is reaching the end of its lifetime. 

  • No air coming from the air conditioning or the heating system 

Another very common symptom of a bad blower motor resistor is when you're dealing with situations where there is no flow coming from the vents. 

A burnt blower motor resistor can make the circuits much shorter, preventing them from functioning and not allowing any air to flow through the system. 

When you notice this symptom, you must immediately replace the blower motor resistor if you would like working heating or air conditioning system. 

  • Air conditioning works at certain speeds only 

Another very common symptom indicating that the blower motor is going bad is when the heating system or air conditioning blows air at certain speeds only.

The air blower motor resistors are designed to operate at different speeds, and when one of these registers goes bad, the air conditioning or the heating system will not work at this certain speed. Thus, if you set the system to a higher speed, you might notice that it's working just fine.

This problem can be very frustrating if you're trying to adjust the air conditioning or the heating system and set it for lower speeds. 

Keep in mind that when the air conditioning or the heating system works at certain speeds, the problem can also be linked to an issue with the switch itself. Therefore, before drawing conclusions and saying that the blower motor resistor needs severe, please, you have also to check the switch and make sure that it's working properly. These two items are actually the primary reason behind air conditioning working at certain speeds only. 

Can I drive my car with a bad blower motor resistor? 

Of course! The blower motor resistor is not a component that affects the drivability of your car. It is most related to the environment and the climate change within your vehicle.

About a blower motor resistor can be very critical if you're driving in environments with extreme temperatures. For instance, if you're driving in cold areas, you need to have a working heating system all the time, and a bad blower motor can be a significant issue.

However, if you live in an area where the environment is not too extreme, you can still live without a working blower motor resistor. 

What causes blower motor resistor failure? 

Like any other component in your car, the blower motor resistor is not designed to last forever, and there will be a point of time where you must replace it.

A bad blower motor resistor can happen in most scenarios due to problems with either overheating or corrosion. 

Also, some people reported that their blower motor resistor got damaged due to excessive electrical current from the rotational speed, which can increase the temperature of the blower motor resistor and damage it. 

How do you bypass a cooling fan resistor? 

According to automotive experts, in most scenarios, a faulty resistor prevents the fan from working at lower speeds. Still, if you can get the vehicle to run the fan at higher speeds, you can bypass a failing resistor.

To do so, you can unplug the wire connections to the resistor and allow your vehicle to request the higher speed immediately without going through there is a stairs job. This way, when you turn on the fan, it will go directly to the higher speed and bypass the lower speed.

How much does it cost to replace a blower motor? 

Blower motor resistor replacement cost ranges from $250 to $800. If your vehicle is still under warranty, you can get the part replaced for only $150.

Of course, labor costs can be significantly different if you're going to a small repair shop instead of a dealership. While that's the case, many owners of modern vehicles still prefer to go to the dealership to ensure that an experienced mechanic well does the replacement part to prevent introducing unnecessary outcomes. 

Many drivers prefer to replace their blower motor resistor to save on labor costs. Still, it is never recommended to do the job yourself unless you are 100% comfortable that you can do the job without introducing any other complications to the system.

How much does it cost to replace a blower motor resistor? 

The price of replacing a blower motor resistor differs significantly depending on your vehicle's type. In general, it should cost you between as low as $3 till as high as $335. 

Blower motor resistor replacement kits come in either one unit, two units, or an additional component within the blower motor resistor kit. 

How long does it take to fix a blower motor? 

According to most automotive experts, if you confirm that the blower motor is bad, not only the blower motor resistor, the job can take up to 2.5 hours. Some areas might only require about 1.5 hours, depending on their availability, final testing, diagnostics, removal, etc. 

Of course, if any other minor repairs need to be taken care of, the process might take longer and might be more expensive. 


Although the blower motor resistor is a very small air conditioning or heating system, its role is beyond critical.

Since the blower motor resistor controls the speed of the blower motor fan, it is the most component that can get damaged over time of use.

When the blower motor resistor gets bad, you must replace it immediately. Otherwise, you will end up without working air conditioning or heating systems. 

It's recommended that you fix the blower motor resistor immediately after it gets that. However, if your vehicle suffers from additional, more complicated problems link to the engine or the transmission, it might not even be worth spending a penny trying to fix the blower motor resistor.

If you are dealing with such a situation, it might be the right time to sell your car to Cash Cars Buyer. Cash Cars Buyer guarantees to buy your car even if it has major issues in the air conditioning system and the engine or the transmission.

Cash Cars Buyer will pay you the top dollars along with free towing despite your living location around the United States.

To learn more about our process and our team, you can reach out to us by giving us a call at 866-924-4608 or visit our home page click on the free instant online offer.

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