A malfunctioning HVAC system during freezing winter days, or insanely hot summer days, is one of the biggest inconveniences. If there is an issue, it needs to be identified and fixed as soon as possible. To do this successfully, you should keep yourself informed about the way your HVAC components function!

Furthermore, there are quite a few things that can affect the system’s operation. Generally, a component breaks and needs to be either repaired or replaced. We will focus on furnace motor blowers, how they work, the most common issues, and whether or not there is a way to fix them. Read till the end for a holistic understanding of the topic!

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How Do Furnace Blower Motors Work?

The primary function of the furnace blower motor is to blow the cooled or heated air through the vents and into your house. The air gets heated by the furnace and cooled off by the air conditioner. Fundamentally, a blower motor needs to provide a current of steady air at a sustainable pressure.

The blower motor consists of the fan assembly, the motor, and the case covering. Moreover, there are two types of drives when it comes to furnace blower motors. These are:

1. Direct drive motors

These are the most commonly found motors in modern gas furnaces. They are connected to the furnace blower wheel.

2. Belt drive motors

They are more often found with older furnaces, and they are not as common in residential furnaces. They operate in a way where the motor pulley is connected to a fan pulley, which is then mounted on a shaft to turn the blower wheel.

Apart from drives, there are also two speeds of furnace motor blowers. These are:

1. Single speed blower motors

As the name suggests, these motors blow at a certain predetermined speed only. It works at a single speed until the room reaches the desired temperature. Once that happens, it turns off until it needs to be switched on again.

2. Variable speed blower motors

They are the opposite of single-speed blowers, which simply means they operate at more than one speed. These are great because they constantly keep the temperature even.

If there is a large gap, it will blow at a higher speed to reach the desired temperature. However, once that happens, it will start blowing at a lower speed.

How To Diagnose a Bad Blower Motor?

Blower motors can work unobtrusively and quietly for years. However, they are under a lot of pressure, especially if they are turned on all the time. This makes them prone to malfunctions, which can be prevented by simply taking care of the device. 

Regular maintenance of your HVAC system, including the blower motor, can help you save a lot of money by avoiding unnecessary costs. Here are some of the things you can do to test your blower motor:

1. Check if it gets enough power

Ensure that there is enough power coming from the board. Check the voltage at the outlet, and make sure that enough power is coming in at the transformer. As a thumb rule, 24V must be going out to the board.

Furthermore, if you notice enough power coming to the board but it is not going out to the motor, this might be a sign that your control board is broken. To test this theory, you can try jumping out 120V to the blower motor wires. Of course, this can only be the case if everything else is fine with the furnace.

2. Check to see if the capacitor is good

This is a little test you can do to see whether the capacitor meets the manufacturer’s specs. If you identify that it does not, you should replace it and try the test again!

3. Make sure that the motor is not too warm

Overheating is not a good sign with any device. However, a blower motor might be doing this due to dust and dirt. If it gets too dirty, it will most likely stop spinning or keep spinning, but the circuit will not be complete. Make sure to regularly clean the blower to avoid this issue!

4. Check the motor’s amp rating

You might have to find a mirror for this one. You should check the sticker on the furnace to see the OEM motor specs, which can vary from 4 to 12. Compare them to amp draws to see if this could be the reason why your blower motor is working intermittently or why the static pressure is too high.

5. See if the motor is spinning

If your motor is experiencing difficulty spinning the rotor that holds the fan blower or is not spinning at all, this probably means that your motor blower is in trouble.

Of course, we have mentioned earlier that there must be enough power getting to it, and the capacitor must be suitable. Make sure to call the technicians if this happens.

6. You hear a screeching sound, but the motor is spinning?

What if the blower motor is moving but making weird noises at the same time? There are quite a few things that could be causing this.

Firstly, center the wheel inside the housing, and tighten the locking nut to the rotor shaft to ensure it does not move around. In addition to this, ensure that the squirrel cage is not touching the side of the blower housing.

7. Check if the blower motor spine is separated from the fins

Fins basically take the air and distribute it further. The air pushing back can cause friction, which will cause terrible sounds. The spine is attached to the rotor shaft, and it spins much faster than the wheel. To solve this issue, try replacing the wheel and doing the test again.


There are a lot of things you can do to test if your blower motor is functioning correctly. Some of the problems you might encounter are solved easily, but others require help from a professional. Do not go around trying to fix things that you know nothing about. We advise you to maintain your HVAC system as it can save you a lot of money and your valuable time!