Blower Motor Resistor Buyer's Guide
- The blower motor resistor has controls that determine air settings, which can reduce or increase airflow if it detects any excess or lacking through the vents via wire coils.
- Each speed setting has its corresponding coil.
- Thinner coils are for higher air settings, while thicker coils correspond to lower air settings.
- The thicker the coil is, the more resistance to the flow of electric current it has—meaning the fan is forced to rotate slower.
- Made of several resistors with varying resistances, the blower motor resistor is connected in series with the blower fan.
- An AC unit running without air, a fan stuck on one setting, and irregular blower fan performance are the symptoms of a bad motor resistor.
- For sweeter deals, shop at CarParts.com, where OE replacement blower motor resistors cost as low as $2, while higher-end products cost up to $320.
- Driving with a worn blower motor resistor could further damage the rest of the system, leaving you with more expensive services.
Can you imagine your car without the air conditioning or heater unit? That’s exactly what we’ve thought of, you can’t. For 86 years, air conditioning and cabin heating, or what was then known as “weather conditioner,” has been an important part of an automobile. Thanks to the Packard Motor Car Company, car cabins became more comfortable than ever.
Air conditioning and heaters give you full control of ventilation using different fan levels. The controls typically come in the form of a dial, though older models feature a lever that can be slid from left to right. The fans are controlled by a control device known as the blower motor resistor.
What is a blower motor resistor?
Before we go deep about blower motor resistors, let’s first discuss what a blower motor is. In able for your vents to pass cold or heated air into the cabin, your cooling or heating system needs a fan. For the fan to work, a blower motor is installed inside the cabin to run the fan. This blower motor has different speed levels that is controlled by a resistor, either by a blower motor resistor or blower control module.
What’s the difference between a blower control module and blower motor resistor, you ask? Cars with manually adjusted AC or heater utilizes a blower motor resistor, while vehicles with automatic climate control feature a blower control module. Blower control modules make gradual adjustments possible in cars with auto climate control. A blower motor resistor, on the other hand, is used in cars with fixed fan speeds.
What does a blower motor resistor do?
The blower motor resistor has controls that determine air settings. It can reduce or increase airflow if it detects an excess or lacking through the vents via wire coils. Each speed setting has its corresponding coil. Thinner coils are for higher air settings, while thicker coils correspond to lower air settings. The thinner the coils are, the less resistance they offer, making the fan turn faster. On the contrary, the thicker the coil is, the more resistance to the flow of electric current it has—meaning the fan is forced to rotate slower.
How does a blower motor work?
Blower fans are typically connected to the battery’s negative terminal or ground on one end, while the other end connects to the positive terminal through a blower motor resistor. Made of several resistors with varying resistances, the blower motor resistor is connected in series with the blower fan. A twist of the knob or selector instantly changes the settings by connecting the corresponding resistor with the right resistance in the blower resistor pack.
Apart from the four to five-speed resistor settings, the blower motor resistor has two extra circuits for the off and highest fan speed state. Lower fan settings allow the blower motor to be disconnected from the power supply. Meanwhile, the other circuit bypasses the blower resistor in the highest fan setting and connects it to the power supply.
How to tell if your blower motor resistor is bad
Have you noticed changes in your vehicle’s air conditioning or heating? Is the air flow getting weaker and weaker day after day? If so, your AC or heating unit needs an assessment so bring it to a certified mechanic. Chances are your mechanic could find out a failing blower motor resistor that’s causing the issue. Here are some early signs of a busted blower motor resistor.
Fan setting is stuck on one speed
The most known sign of a failing blower motor resistor is a blower motor that’s stuck on one speed and won’t function when switching to other settings. Since the blower motor resistor is responsible for controlling the fan speed, it’s possible that it can’t adjust the speed when it begins to malfunction.
AC unit running but no air through vents
The blower motor is fed with power by the blower motor resistor. If the resistor malfunctions, it may fail on supplying the motor with enough power to activate the fan. This then leads to no airflow coming out of the vents no matter how hard you crank your AC control switch since the motor can’t produce enough air pressure.
Irregular fan performance
You might notice a late activation of the blower fan every time you start your vehicle when your blower motor resistor begins to fail. This is often due to large connector gaps in the bad blower resistor motor, which limits it to only activate when there’s higher supply of electric current. The fan may die again when your car’s at cruising speed, as the electrical flow diminishes again.
No lower fan settings
A failing blower motor resistor may develop larger gaps in between the connectors. Since lower AC or heater settings require less electric charges, the gaps will make it harder to jump from one connector to the other. This leaves the higher settings functional as high-voltage electric current may still be able to travel through the connectors. If your resistor’s condition diminishes greatly, it will leave the car blower not working on all settings.
You can read more information in our article "How to Test a Blower Motor Resistor".
Importance of replacing a broken blower motor resistor
Ignoring a damaged blower motor resistor may lead you to bigger AC or heater-related problems. Driving with a worn blower motor resistor could further damage the rest of the system, leaving you with more expensive services. A cool or heated cabin during extreme weather conditions is important to keep you and your passengers comfortable and at peace. Lastly, it’s always better to have full control of the cabin’s temperature at all times for convenience.
Things to Consider When Buying a New Blower Motor Resistor
Have you had enough with either having to turn off your AC system or enduring freezing cold because of a faulty blower resistor? Are you stuck with a car air-conditioner that only blows cooling air at a high speed? If you are, then it's about time you replace a faulty blower motor resistor with something that works. Here are a few dos and don'ts to help you in shopping for the right one.
Blower Resistor Type
There are basically two types of blower motor resistors, one that uses coils and another that uses transistors. If you're driving an older car, then chances are it's fitted with a coil-type resistor. Modern cars, on the other hand, usually have blowers that are transistorized. You can also double-check the type of resistor you have by looking at the part itself. If you see a number of wires hanging from the part, then you'll need to get a coiled one. But if the resistor is simpler in design, then get one with a transistor.
Number of Blower Resistor Terminals
Blower motor resistors vary according to the number of prong terminals that they have. They can have either 6, 4, or 3 prong terminals. Just to be sure that you get the right kind, always compare the new one with your old resistor. This will ensure optimum compatibility and smoother, more efficient operation once the part is installed.
The standard for this kind of part is for a period of 1-year with an unlimited-mileage. So make sure you don't get anything less. Remember, it's better to get a good warranty to get the best value out of your part.
How much is a blower motor resistor?
If you are in the market for a blower motor resistor replacement, allot a budget of up to $100 to $160. For sweeter deals, shop at CarParts.com, where OE replacement blower motor resistors cost as low as $2, while higher-end products cost up to $320. Products are sold individually or as part of a kit.
To narrow down your search, indicate the year, make, and model of your vehicle on the filter tab. You can further customize the list by choosing from the categories listed under the “Refine By” menu.
How to Install a New Blower Motor Resistor
Do you find it annoying when your blower fan is working only at one speed? If you feel like you're not getting the most out of your A/C unit because of a faulty blower motor, then you should start thinking about replacing your blower motor resistor. Here's a sure-fire way to help you replace your new resistor with ease:
Difficulty level: Easy to moderate
Things you'll need:
- New blower motor resistor
- Socket wrench
Step 1: Before working on anything electrical inside your car, be sure to disconnect your battery's cable. Open the hood of the car and locate your battery. Using a socket wrench, remove the negative cable on your car's battery.
Step 2: Open your passenger's side door. To give you space while working on your A/C system, push back the passenger's seat. Lie down in a position where you can see the parts inside your dash.
Step 3: Know where your blower motor is. The blower motor is located within your dashboard. It's a black cylinder with wires and hard plastic tubes connected to it. Within your blower motor is your blower motor resistor. It is the smaller plastic box attached to your blower motor. If you still can't find it, follow the wire harness connected to your blower motor. You should be able to find your way through the resistor.
Step 4: Now that you've located both your blower resistor block and its wiring harness, press the tab on the plastic harness and pull it off. This will unplug your wiring connector from your blower resistor block.
Step 5: After disconnecting the two parts from each other, unscrew your faulty resistor block from your blower motor and discard it.
Step 6: Install your new blower motor resistor in place. Follow steps 3 to 5 in reverse order to complete your installation.
Step 7: Reconnect your battery cables and start your car to check the blower motor resistor.