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What is the Blower Motor Resistor?

Author: Apogeeweb
Date: 27 Aug 2021
 1486
blower motor control module

ⅠIntroduction

 

Resistor is commonly used in our daily life. There are all kinds of resistor in a vehicle. As we know ,the air conditioning is very important for a car . One of the most essential components is blower motor resistor. This article embodies basic knowledge about blower motor resistor.

location-in-a-car

Figure1: the location of Blower Motor Resistor

 

ⅠIntroduction

ⅡDefinition and Function of Blower Motor Resistor

2.1 Definition of Blower Motor Resistor

2.2 Function in a Car

Ⅲ How the Blower Motor Resistor Works?

Ⅳ Symptons of Faulty Blower Motor Resistor

Ⅴ Blower Motor Resistor Test

Ⅵ How to Replace Blower Motor Resistor

6.1 DIY Jobs Related to the Blower Motor Resistor

6.2 Details of Replacing Blower Motor Resistor

Ⅶ Frequently Question Asked about Blower Motor Resistor

 

ⅡDefinition and Function of Blower Motor Resistor

 

2.1 Definition of Blower Motor Resistor

The heating and air conditioning system in your vehicle is made up of many parts that work together to produce the desired air temperature. Some of these parts will (hopefully) last the life of your vehicle, but others will wear out and need to be replaced.

The blower motor resistor is a small electrical component that, if it fails, can cause noticeable problems with the air in the passenger compartment. Understanding how it works can assist you in identifying the symptoms of a faulty resistor.

This vedio shows a circuit of a blower motor

 

 

2.2 Function in a Car

A blower motor is a device that drives the fan in a car's heating and air conditioning system. It's usually found inside the dash, on the opposite side of the steering wheel, or on the firewall inside the engine compartment. A blower motor resistor, also known as a blower motor control module, is the component that regulates the speed of the blower motor.

An electronic blower motor control module is fixed in cars with automatic climate control systems and vehicles where the blower speed can be gradually adjusted.

 

 

the-module

Figure2: the control module

 

The blower motor resistor or control module is usually installed inside one of the ducts in the HVAC system, close to the blower motor, in most modern vehicles. This is done so that the resistor or control module can be cooled by passing air. A blower motor resistor was installed on the firewall of some older vehicles, with access from under the hood.

 

Ⅲ How the Blower Motor Resistor Works?

Blower motor resistor diagram depicts how the blower motor resistor is connected in a typical automobile. The resistor is bypassed in this car at the highest "4" fan speed setting, and the blower motor is powered directly by the fan switch. As a result, even if the resistor is faulty, the blower motor in some vehicles may continue to operate at a "High" speed.

The fan switch is set to "1" in this diagram, so the blower motor current is reduced by three resistors (R2 + R3 + R4) connected in series. The flow of current is depicted in blue and red.

Two resistors are connected in series when the setting is 2.  Whereas, in setting "3," there is only one resistor. When resistance is added to an electric circuit, the current in the circuit is reduced. When multiple resistors are connected in series, the total resistance rises and equals the sum of the individual resistances.

 

how-the-motor-works

Figure3: how the blower motor resistor works

 

 

Ⅳ Symptons of Faulty Blower Motor Resistor

A faulty blower motor resistor can disrupt the operation of the entire heating and cooling system. A bad or failing blower motor resistor will usually cause a few symptoms that will alert the driver to a potential problem. It is critical to understand the symptoms of a faulty motor resistor.

 

1. The blower motor is stuck at one speed.

A blower motor that is stuck on one setting is a common symptom of a faulty blower motor resistor. The blower motor resistor is the component directly responsible for controlling the fan speed of the blower motor. If the resistor shorts or fails, the blower motor may become stuck at one fan speed. The heating and air conditioning systems may continue to operate at one speed, but the resistor has to be replaced before full functionality can be restored.

 

2. The blower motor does not operate in certain settings.

A blower motor that does not function in certain settings is another common symptom of a faulty blower motor resistor. If the internal components of the blower motor resistors fail, the blower motor may malfunction or not function at all on one or more of the settings. Perhaps, a faulty blower motor switch can lead to the same situation, so a proper diagnosis is highly recommended if you are unsure of the problem.

 

3.There is no air coming from the vehicle's vents.

Another sign of a faulty blower motor resistor is the absence of any air from the vehicle's vents. Power to the blower motor is routed through the blower motor resistor, so if it fails or has any problems, power to the motor can be cut off. A blower motor that is not powered will not have the capacity to produce any air pressure, leaving the heating and air conditioning system with no air coming from the vents.

Because the blower motor resistor is the component directly responsible for powering the blower motor, when it fails, dangerous problems with the blower motor and the heating and air conditioning system can occur. If your vehicle exhibits any of the symptoms listed above, or you suspect that your blower motor resistor is malfunctioning, have it inspected by a professional technician, such as one from YourMechanic, to determine if the component needs to be replaced.

 

Ⅴ Blower Motor Resistor Test

Firstly, if the blower motor does not work at all, it is necessary to test the motor. When the blower motor is turned on, the voltage at the blower motor connector is typically measured. If there is a voltage at the motor (at least 4-6 Volts at low speed and 12 Volts at high speed), but the motor does not run, the motor is defective or jammed. Voltage testing of the blower motor The voltage at the blower motor is being tested. If there is a voltage at the motor (at least 4-6 Volts at low speed and 12 Volts at high speed), but the motor does not run, the motor is defective.

how-to-test

Figure4: how to test the blower motor resistor

 

Leaves, twigs, nuts, and pieces of a ripped cabin filter can jam the blower motor's blade. This is a common occurrence in many automobiles.

The entire blower motor circuit, beginning with a fuse, has to be tested if the motor is in the case of no voltage. See also: how to test a fuse in a car.

If a blower motor fails, it must be replaced. Depending on the vehicle, the cost of replacing the blower motor ranges from $320 to $650. In many cars, the blower motor is located behind the glove box and is held in place by 3-4 screws. In others, it may be located inside the dash (as in the Mazda 5), making replacement difficult.

 

Ⅵ How to Replace Blower Motor Resistor

While you're under the hood working around the HVAC housing, here are some related tasks you should complete for preventative maintenance or to avoid future HVAC system problems.

Take out and clean the blower motor fan.

Replace the cabin air filter.

 

the-fan

Figure5: the blower fan

 

6.2 Details of Replacing Blower Motor Resistor

The following are the simple steps to replacing a blower motor resistor: 

1.Locate the Blower Motor Resistor

Obviously, the first thing you had better do is locate the blower motor resistor so that you determine which component will be taken out. It is directly next to the blower motor. The latter, on the other hand, is commonly found underneath the passenger side dash or in the engine compartment.

 

2.Take out the Blower Motor Resistor

Remove the blower motor resistor now that you know where it is. To begin, remove the components surrounding the blower motor resistor, including the pigtail connected to the AC and the blower motor cooling duct. You can now easily access the blower motor resistor at this point.

All that remains is to unscrew the bolts that hold the blower motor resistor in place. Using a ratchet with a short extension, tighten the screw. Once the bolts are taken out, all that remains is to remove the blower motor resistor.

 

3.Disconnect the Wires

After removing the blower motor resistor, cut the wires that connect to the component. Cut the wires with a stripper or scissors designed for cutting through wires.

 

4.Install the New Blower Resistor

Apply dielectric grease to the housing of the blower motor resistor before proceeding with the installation. It will keep water out of the vehicle, which is a common issue when driving off-road. Apply a coating around the plastic to create a seal that will protect the component.

Replace the blower motor resistor in the same location where it was previously removed. Replace the screws to secure them in place. Connect the pigtail when you are finished with the job. However, there are some cases in which the pigtail has already worn out. Proceed to the next step if this is the case.

Disconnect the old wires and reconnect the new ones. Because the wires are probably color-coded, this should be simple. Connect the new wires with the connectors. Return the pigtail to its original position, and you fulfill the task.

Ⅶ Frequently Question Asked about Blower Motor Resistor

1.What does a resistor do for a blower motor?

Blower resistors are resistors which are used to control the fan speed of automotive blowers. The fan speed can be changed either by switching the blower resistor resistance mechanically using a rotating lever, or electronically by the air conditioning system.

 

2.Why do blower motor resistors fail?

In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.

 

3.Can you fix a blower motor resistor?

The resistor module is easy and inexpensive to replace. It's then typically installed in the ductwork, near the car blower—either under the dash or under the hood. (Refer to a service manual to locate yours.) Purchase a new resistor module at the auto parts store (usually less than $25).

 

4.Can you drive with a bad blower motor?

A bad heater blower motor will not affect the safety of your car, with the possible exception of you not being able to clear the windshield of snow, ice, or condensation if the defrosters don't work. But you won't be comfortable inside your car, especially during the cold of winter and the heat of summer.

 

5.How do I know if my blower motor has power?

Check for power at the motor itself. Using a test light or a multimeter set on volts, unplug the blower motor. Keeping the black lead on a good ground, usually a bolt on the engine block, and the blower switch turned on, use the red lead to probe the plug that usually attaches to the blower motor.

 

 

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