Blower motor resistor how does it work

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. 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.

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.

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. 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 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. Figure3: how the blower motor resistor works. 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. 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. 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. 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. 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 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 Volts at low speed and 12 Volts at high speed , but the motor does not run, the motor is defective. Figure4: how to test the blower motor resistor.

The blower motor resistor is an electrical component that is a part of the vehicle's heating and air conditioning system.

When fan speed is changed via the knob on the instrument cluster, the blower motor resistor changes setting, which changes the speed of the blower motor. As the fan speed is one of the most frequently adjusted settings of the air conditioning system, the blower motor resistor is put under constant stress, which can cause it to eventually fail.

A failed blower motor resistor can cause issues with the operation of the entire heating and air conditioning system. Usually a bad or failing blower motor resistor will produce a few symptoms that can alert the driver of a potential issue.

A common symptom of a faulty blower motor resistor is a blower motor that is stuck on one setting. The blower motor resistor is the component directly responsible for controlling the blower motor fan speed.

If the resistor shorts or fails, it may cause the blower motor to remain stuck on one fan speed. The heating and air conditioning systems may still function at one speed, however the resistor will have to be replaced in order for full functionality to be restored.

Another common symptom of a faulty blower motor resistor is a a blower motor that does not function on certain settings. This can also be caused by a blower motor switch, so a proper diagnosis is highly recommended if you are uncertain of what the issue may be. Power to the blower motor is fed through the blower motor resistor, so if it fails or has any issues power can be cut off to the motor.

A blower motor without power will not be able to produce any air pressure, and as a result the heating and air conditioning system will be left with no air coming from the vents. As the blower motor resistor is the component directly responsible for powering the blower motor, when it fails it major issues with the blower motor and the heating and air conditioning system can be experienced.

If your vehicle is displaying any of the symptoms above, or you suspect that your blower motor resistor may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the component should be replaced. This article originally appeared on YourMechanic. Autoblog is partnering with YourMechanic to bring many of the repair and maintenance services you need right to you.

An OL reading on a multimeter likely indicates a full break in the circuit, meaning the resistance is too great to read from one test to another.

The higher the reading, the more resistance there is. Static resistors are designed to supply current at a constant level under specific resistances. When they fail, they supply either too much or too little current to a component. The heating and air-conditioning system uses several resistors to supply the desired airflow by sending power to the blower motor.

The more power supplied, the higher the fan speed and the stronger the airflow. The blower motor resistor is a single part, often with several possible pathways for current flow that provide more or less resistance, depending on the demand from the dash setting. When it fails — usually due to corrosion or overheating — you may notice a few things:. Take time to determine the cause of your airflow woes before replacing parts. Replacement of each component varies in difficulty depending on the vehicle, but an experienced DIYer can do it at home comfortably.