Why does a fan need a resistor?

Why does a fan need a resistor?

It is responsible for controlling the blower motor’s fan speed. 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.

What does cooling fan resistor do?

The cooling fan resistor is meant to send power to the fans in steps, so that the fans may operate at different speeds. If any of the individual steps or switches fail, it will disable the cooling fans from operating on that speed setting.

How much resistance should a blower motor resistor have?

According to the service manual, it must be around 4-5 ohms. In our case the ohmmeter shows open circuit, which means the resistor has failed. Sometimes, a blower motor resistor might fail due to problems with the blower motor itself.

Do you need a blower motor resistor?

As we mentioned earlier, a blower motor resistor isn’t necessary in two instances. When the fan is off completely, or when the fan is running at high power. At high power the current bypasses the resistor because it doesn’t need to be modulated it anyway.

How do you know if a fan resistor is bad?

Here are some of the warning signs of a bad heater blower motor resistor:

1. Fan does not work at all, so no air comes out of the vents.
2. Fan only works on some speeds and not others.
3. Fan only works on the highest speed.
4. Fan runs all the time and can’t be controlled with the fan switch.
5. You see smoke coming out of the vents.

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).

How can you tell if a blower motor resistor is bad?

Symptoms of a bad heater blower motor resistor

1. Fan does not work at all, so no air comes out of the vents.
2. Fan only works on some speeds and not others.
3. Fan only works on the highest speed.
4. Fan runs all the time and can’t be controlled with the fan switch.
5. You see smoke coming out of the vents.

How does a blower motor resistor work in a car?

This is done, so the resistor or a control module is cooled down by passing air. In some older cars, a blower motor resistor was installed on the firewall with the access from under the hood.

What happens when a heater motor resistor fails?

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. 2. Blower motor does not work on certain settings

How can I tell if my blower motor resistor is faulty?

Another symptom of a faulty blower motor resistor is no air from the vehicle’s vents at all. 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.

Why does my blower only work on high speed?

However, most car makers bypass the blower motor resistor completely when you move the fan speed switch to high. If your blower only operates on its highest speed, chances are you have the series type of blower motor resistor. This is the most common failure mode. To repair the problem, simply replace the resistor block.