The blower motor on your furnace plays a critical role in the heating process and even has safety functions to protect you and the furnace.
For this reason, it helps to know more about the blower motor, such as where it’s located on the furnace, precisely what it does, what could go wrong with the fan, and how to troubleshoot and DIY-fix your fan. That’s what this guide is all about.
What is a Blower Motor?
The furnace’s blower motor or fan is a specialty fan built into the furnace to help draw cold air into the unit and push out warm air into the home. It’s typically a hamster-shaped metallic device comprising a motor with wire coils at the center and a wheel with attached blades.
When the motor rotates, the blades rotate in tandem, causing the air motion necessary to draw cold air into the furnace and expel warm air.
What Does the Blower Do in a Furnace?
The furnace blower has multiple responsibilities, including ensuring maximum energy efficiency. However, its three main functions are;
- To draw cool air into the furnace: The furnace works by getting cold air from the home, warming it, and sending it back. It’s the blower fan’s duty to draw the cold air.
- Blow warm air back into your home: The fan also generates the airflow necessary to push warm air out of the furnace, through the ductwork, and into your home.
- Evenly circulate warm air throughout the home: The fan also initiates and sustains the air circulation necessary to evenly disperse warm air to every corner of the home.
Where is the Blower Motor on a Furnace Located?
The furnace blower motor is located in the furnace’s base compartment. You’ll find it just behind the air filter, which sits in front of the return air vent. The return vents are located behind the grill through which cold air enters the furnace.
The location is strategic as it allows the blower fan to exert enough force to pull unconditioned dense air through the filter and push it at pace over the heat exchanger.
The airflow speed is also sufficient to force warm conditioned air through the ductwork and into your home. To find the blower motor, remove the front panel and then the bottom panel.
Then check in the base compartment. Most blower fans come inside a metallic casing supported on the bottom rails.
How the Blower Fan Works
The blower fan’s working mechanism is straightforward. The fan first comes on several seconds or more than a minute after the furnace’s burners light up. Specifically, it comes on when the temperatures within the furnace hit 100° F.
At this point, the limit switch closes, allowing electricity to flow to the fan. The motor then starts, and the fan blades follow. Under normal circumstances, the fan will run until several minutes after you shut down the furnace. Sometimes you can hear the fan spinning 30 minutes after switching off the furnace.
It goes off automatically when temperatures inside the furnace drop below 90°F. The limit switch will open at this point, cutting the electric supply and effectively shutting the blower fan. However, the limit switch may also open if the fan or furnace encounters abnormal operation, such as overheating.
For instance, most blower fans will go off if temperatures inside the furnace exceed 200°F.
What are the Symptoms of a Bad Blower Motor?
The symptoms of a bad blower motor vary depending on the underlying issue. However, you want to keep an eye out for the following;
- The furnace is suspiciously quiet: All furnaces make a low humming sound when running. In fact, the gentle hum is one of the signs of a perfectly working furnace. Therefore, if the unit suddenly goes quiet, something is up – and it’s most likely the blower motor.
- Strange noises: On the other extreme, a faulty blower motor can also make loud, strange noises. A loud screeching noise, for instance, can point to broken or bent blower blades grinding against the blower housing. Meanwhile, a wheezing noise can be a sign of a bad motor.
- The furnace doesn’t blow warm air: If your furnace is ON and the thermostat is calling for heating, but you can’t feel any warm air at the supply ducts, the furnace blower motor could be broken or dead.
- Furnace stops suddenly: AS we mentioned earlier, one of the responsibilities of the blower motor is to “trip” the furnace in case of overheating. Interestingly, a broken blower motor could also be the source of overheating. So, if your furnace goes off suddenly, you should check the blower motor.
Reasons Your Furnace Blower Motor Won’t Turn ON
If you observe one or more of the signs above and later suspect that your furnace blower motor won’t turn ON, it could be due to the following reasons;
The blower motor isn’t getting power
The motor gets power directly from the furnace’s circuitry. Thus, it can lack power even if the rest of the home has power. You want to probe the wiring for loose connections and the circuit board for damage.
The blower fan capacitor is dead/aging
Although the fan draws running power from the circuit board, it relies on a dedicated capacitor (typically 200V to 400V) for starting power. Therefore, the fan cannot start if the capacitor is broken, dead, or missing.
The limit switch is open
The blower motor can only run if the limit switch is closed. So, anything that causes the limit switch to remain open may cause the blower motor to stay off. Common reasons include a stuck switch (perhaps because of dirt buildup) and switch damage.
The fan has internal damage:
The blower motor fan comprises multiple components that work together to keep your furnace going. These include the motor, blades, belt, etc. The furnace may not run if any of these parts are broken.
How Long Does a Blower Motor Last?
The furnace blower motor can last 10 to 20 years with proper maintenance. That’s because most motors are durable components built from stainless steel.
However, this means that you need a high-quality furnace for maximum blower motor life. Also, only replace the motor with original equipment manufacturer parts.
Otherwise, you may have to replace the fan more frequently.
How to Reset a Furnace Blower Motor
If your blower motor has refused to start or shows signs of failure, the first thing you should consider is to reset it. Resetting the blower motor gives it a chance to auto-resolve internal issues. Fortunately, it’s easy to reset a blower motor;
- Switch off the furnace at the breaker and turn off the gas supply at the main valve. Then allow the blower to cool off completely.
- Remove the front cover then the blower compartment cover to access the blower. You may or may not need a screwdriver.
- Locate the reset button on the blower. Typically, it’s a red or yellow switch on a rounded part on top of the blower fan housing.
- Press the reset switch for five to twenty seconds, then release it. Feel free to refer to your owner’s manual for more details.
- You’ve just reset the blower motor. Now, replace the panels, turn the gas supply back on, switch the breaker on, and switch on the furnace to see if the original problem is gone.
How to Replace the Furnace Blower Motor
If the blower still doesn’t run, it may be damaged. You can take it off for more inspection and general cleaning. Cleaning the blower motor is as simple as scrubbing away the dirt and debris using a toothbrush.
If cleaning doesn’t help, use a multimeter to test the blower for continuity and replace it if it’s broken or aged. A replacement blower costs about $20, while professional replacement costs start from around $80.
That’s it. Now you know the role of the blower motor in your furnace, where it’s located, and how to troubleshoot it. Don’t hesitate to seek professional services whenever it becomes necessary.