A blower motor resistor is an integral part to your heating and cooling system and its ability to be adjusted to your preference. It helps control the speed of the fan that pushes the conditioned air into the cabin. The fan speed is normally one of the most adjusted features in a vehicle and thus, places a high demand and stress onto the blower motor resistor function. This can eventually cause the component to fail. Without its functionality, a failed resistor can cause the entire system to not work properly or can cause other components to fail.

How Does A Blower Motor Resistor Work?

When you use the heating or cooling feature in your vehicle, a fan turns on and you can feel the appropriate temperature air come from the vents. This can happen thanks to a device called a blower motor. Most often it can be located inside the dash on the passenger side of the vehicle. Other times you can find it inside the engine compartment attached to the firewall.

Modern automobiles allow you to adjust the speed of the blower motor giving you different settings of comfort by letting you choose how forceful the air comes out of the vents. The reason you can do this is because the resistor gives you a way to regulate the speed by lowering or raising the voltage that is sent to the fan. The blower motor resistor can usually be found under the dash as well. It will be located between the heater and air conditioning control knobs and the blower motor itself. More than likely, it will be attached to the ducting near the blower motor so that it is kept cool while it is in use.

There are typically two types of blower motor resistors. The first type uses different sized wire coils with different resistances in correlation with each speed setting. These are more often part of older vehicles. The second type utilizes transistors and a circuit board to send information through fully integrated circuits. You will find this is the type more often used today.

How to Tell When You Need to Replace Your Blower Motor Resistor

Like any other component in your car, the resistor is not immune to breaking down eventually. How do you know it is the culprit and what signs do you look for to tell if it needs a replacement? Here are some characteristic symptoms to look for:

  • Speed. On most vehicles, the default setting for the blower motor is on its maximum setting. If you find that you cannot lower the setting to something besides its highest, then the blower motor resistor is likely to blame.
  • Wire Damage. When the blower motor fails, it will usually draw a lot of power from the electrical system and become very hot. Most times this will present itself as melted areas on the wire harness.
  • Blower Motor. Sometimes, when the blower motor goes bad, it will try to draw too much power from the blower motor resistor and cause it to fail too. Thus, you will need to replace both parts in this scenario.
  • Leakage. If you notice a heater core that is leaking fluid, it may cause a blower motor resistor and blower motor to fail as the fluid will leak into the vehicle and onto these components.
  • Inspection. Upon visual inspection, many times you can see areas of corrosion that have caused it to fail.
  • Resistance. If you do not see indications of corrosion, you can check the resistance between the terminals with an ohm meter. It should read 4 to 5 ohms. An open circuit is a sure indication of failure.

Cost of a Blower Motor Resistor

Many things go into pricing any repair on your vehicle. Here are some typical costs to take into consideration if you are thinking about a repair.

  • Parts. If you are a DIYer, you can save about 50% of the mark-up cost when ordering online compared to having a shop order the part. If you order yourself, you can usually find a new blower motor resistor for 15 to 35 dollars. Double the cost for “at shop” parts.
  • Labor. Labor cost varies at each mechanic shop. Hourly fees apply and can really ramp up your total cost.
  • Overall cost. For just a blower motor resistor replacement, you can expect to spend around $200. Again, depending on the part cost and labor rate.
  • Other parts. Finding that other parts caused the blower motor resistor to fail, or that its failing caused other parts to need a replacement, will obviously cause your total bill to go up.

Can I Replace the Blower Motor Resistor Myself?

Many opt to replace the resistor themselves. It is an easy part to replace, even for novices. Usually, you only need a few tools and a little time. Here is a general repair guide:

  • Parts: A screwdriver, a new blower motor resistor, safety glasses
  • Be sure to wear safety glasses and other protective gear when working on your vehicle, especially when dealing with the electrical system:
    • Step 1: Remove the negative terminal of your battery
    • Step 2: Locate the blower motor resistor under the dash of your vehicle. You can find it next to the housing ducts near the blower motor.
    • Step 3: Remove the electrical connector that is attached to the resistor
    • Step 4: Remove the screws (sometimes bolts) that hold the resistor onto the housing.

Examples of Blower Motor Resistors

Duralast DR798

Duralast puts their resistors through rigorous testing to ensure their durability and performance. Reviewers notice the effort and appreciate the ease of replacement.

  • OEM fit;
  • 4 Blade Male Connection;
  • High-Quality Materials including copper alloys.

Crown Automotive 5012699AA

Crown Automotive has become a go-to company for many DIYers looking for premium quality replacement Jeep parts. Reviewers cannot say enough about the incredible efficiency of this part.

  • Direct fit;
  • Has auto temperature control;
  • Exceeds original specs and performance.

Dorman Techoice 973

Dorman is a leading supplier of OE aftermarket parts that are top-quality. Reviewers love the perfect fit.

  • Comes with new harness;
  • Corrosion resistant;
  • Prevents burnout and thermal fuse failure.

Conclusion

If your heater or AC just isn’t working quite right, or you cannot adjust the fan speed, your blower motor resistor may be to blame. Through a few simple troubleshooting suggestions and minimal time and effort, you can diagnose and replace your own blower motor resistor and get the comfort of your cabin back.

What is your experience with replacing blower motor resistor? Leave any helpful hints and comments below.

Image: depositphotos.com.

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