Worried your furnace blower motor is going back, but aren’t sure how to check it? Look no further!
Signs of your furnace blower motor not working include: a burning smell coming from the vents (or the furnace itself), or heard unusual sounds coming from your furnace (often described as a “humming”).
Maybe your furnace only works intermittently, or conversely, the furnace seems to be running all the time, but the house is still cold!
These are all signs that your furnace blower motor is going bad. There are a few ways you can know for sure – just read on!
In this guide you’ll learn
- What is a furnace blower motor?
- Supplies you’ll need to check your furnace blower motor
- How to locate the blower motor in your furnace
- How to check the blower motor (with and without a voltage meter)
What You Need To Know About Checking your Furnace Blower Motor
What is a furnace blower motor?
The furnace blower motor is responsible for circulating air throughout your home; it blows the air heated by your furnace throughout the vents to ensure the home reaches the temperature called for by the thermostat.
The motor looks like a large cylindrical electrical component encased by a metal bracket and attached to the blower wheel.
Strictly speaking, the blower wheel is what circulates the air, and the wheel is powered by the blower motor.
Supplies You’ll Need To Check your Furnace Blower Motor
- Non-Contact Voltage Tester – This inexpensive and easy-to-use tool lets you quickly and safely confirm that all power has been shut off to your furnace.
Use the voltage tester before touching any of the electrical components of the furnace (more information below). There are several types of voltage testers, but we recommend a non-contact tester because of their safety and ease-of-use.
- Voltage Meter – The voltage meter is used to test whether power is getting to your blower motor.
There are other ways to determine if your blower motor is going bad (more on that below), but using a meter is the only way to know for sure.
How To Check your Furnace Blower Motor (7 Steps)
Step 1: Turn off all power to the furnace
The first thing to do before you can check your blower motor is turn off your furnace power switch, if you have one.
No furnace power switch? Turn the power off from your breaker box (just be sure the gas is turned off before turning off the breaker).
Step 2: Remove the Furnace Access Panels
The access panels (sometimes simply called the “doors”) protect the internal components of the furnace. Your furnace may have screws that hold it in place, or may simply slide off.
Note, The furnace blower motor is generally located in the bottom compartment of the furnace (behind the bottom door).
Step 3: Use your voltage tester to ensure no electricity is flowing through the furnace
Lightly touch the end of your voltage tester to each electrical wire in your furnace to confirm electricity is not flowing through the furnace.
If you haven’t used this voltage tester before or don’t know how to use one, a quick test is to tough the tester to an electrical wire that you know does have electricity.
The light at the end of the tester will light up if there is electricity flowing through the wire.
Once you’ve run the tester along each wire and know all electricity has been shut off, move on to the next step.
Step 4: Feel the area near the blower motor to determine if it’s hot
With the power off, try to feel around the back of the furnace compartment that contains the blower motor. Be careful while performing this step as the blades of the blower wheel can be sharp.
If that area is hot, there’s a good chance your blower motor is causing the problem. If it’s been a while since you tried to run your furnace, the blower motor may have naturally cooled off. If you aren’t sure, try running the furnace and repeating the above steps.
This is the best educated guess you can get about whether your blower motor is causing issues for your furnace without a voltage meter.
If you have a voltage meter, read on!
Step 5: Disconnect the appropriate fan wire and your common wire
The furnace compartment that contains your blower motor also contains the control board.
The control board is in charge of all electrical operations for the furnace, so you likely have 12 – 15 wires running throughout this part of your furnace.
Two (or maybe three) wires run from the control board to blower motor. Find those wires and make a note of where they plug into your control board.
Check the print on the circuit board to determine which of those wires is connected to cooling and which is connected to heating.
With the power turned off, disconnect the wire associated with the same setting being called for by the thermostat (for example, if your thermostat is calling for heat, disconnect the wire connected to heating; if your thermostat is calling for cooling, disconnect that wire).
Next, locate what is known as the common wire on your control panel.
The details of what the common wire is isn’t important, but you can typically locate it by again referring to the text on the control panel itself (look for “CIR”, “CIRC”, or “CIRCULATOR” on the control panel.
With the power turned off, disconnect that wire.
Step 6: Return power to the furnace
For this next step, use the voltage meter to test whether electricity is getting to our blower motor, so return power to the furnace before proceeding.
Step 7: Test whether your furnace blower is getting power with your voltage meter
With the power to the furnace on, gently place each end of the meter lead into the outlets for the wires you just removed.
If power is getting to the blower motor, you should see 120 volts displayed on your voltage meter.
If you see 120 volts on your meter, but your blower motor hasn’t been starting, then it’s very likely your blower motor is the culprit.
You should now have a very good idea of how to check your furnace motor blower and determine whether it’s responsible for your faulty furnace!