How To Know if Furnace Blower Motor is Bad

A bad inducer motor can mean a few nights in the cold unless you fix the issue promptly. Fortunately, sometimes the problem is as simple as loose wires that you can reattach and resume heating within a few minutes. Or it could be an even more trivial matter, such as a dirty flywheel that you can clean within seconds.  

The big challenge, however, is confirming that it’s indeed an inducer motor problem. How can you tell for sure that you have a bad inducer motor? Let’s find out.

How to Know if Furnace Blower Motor is Bad

No Humming Sound when you Start the Furnace

The first thing you should keep an ear out for is the low humming sound that begins immediately you turn on the furnace. It’s not as loud as the humming from the blower motor as the blower motor is much bigger. However, you can hear the sound if you listen carefully.

Remember that the draft inducer motor comes on immediately when you turn on the furnace, unlike the blower motor that starts up to two minutes later. Can you hear the sound? If not, then maybe the draft inducer motor is bad and thus not spinning.  

Strange Loud Noises when you Start Furnace

Here too, you must listen to the first sounds that come out immediately you turn on the furnace. If the sound is louder than usual, you may have a bad draft inducer fan.

A screeching sound usually means that one metallic part is running against another, meaning that you’re dealing with broken blades or one of the parts has become loose.

Meanwhile, a wheezing noise or overly loud hum means that the motor is dead. You’ll need to be very keen to hear the sounds as the blower motor’s sounds may soon overpower the draft inducer noise. Standing next to the furnace for at least a full minute after pushing the ON button may help.

Furnace Starts then goes Off Abruptly  

You likely understand that the draft inducer motor removes exhaust gases from the furnace, especially the heat exchanger, to enable safe heating.

Thus, a defective or bad draft inducer motor poses a massive risk to the home’s occupants. For this reason, furnaces have a pressure switch that automatically shuts the furnace if the blower motor isn’t working.

If issues #1 and #2 above are followed by the furnace going off, then you almost certainly have a bad draft inducer motor. However, beware that the two issues above may not be as pronounced as you wish. So, the furnace may seem to go off abruptly. Typically, it will shut down within under two minutes of coming on.

Furnace Refuses to Come on Altogether

Other times the furnace may refuse to come on altogether. This often happens after trying to restart the furnace several times to no avail and is known as furnace “lockout.”

A lockout is a non-responsive state where the furnace refuses to take most external commands until you reset it.

It will not even attempt to come on, no matter how many times you try. The good news is that it’s not too difficult to find out whether your furnace has entered lockout, as most furnaces will give an error code requesting a reset. You should consider resetting it anyway, even if you don’t see relevant error codes.

Pressure Switch is Perpetually Open

The draft inducer motor works side by side with the pressure switch to ensure safe heating free from poisonous exhaust gases. The pressure switch closely monitors the draft inducer switch’s operation by closely monitoring pressure levels. It follows, therefore, that a broken draft inducer motor can impact the pressure switch too.

Specifically, if the draft inducer switch is dead or broken, it cannot generate enough negative pressure to close the pressure switch. Thus, the switch will remain open perpetually. Be careful not to mistake it for a damaged pressure switch.

Here is how to tell if your furnace pressure switch is bad?

Evidence of Physical Damage

You can also check the inducer motor physically to see if it’s damaged. To do this, with the furnace off, locate the motor and check whether the two wires connecting to it are instant.

If so, check the cause for damage. Is the flywheel intact? Are the blades in place? If you notice a broken blade, then the blower motor may not function normally.

Also, try to rotate the flywheel. It should rotate freely. If something obstructs it, find out what it is. Is it dirt buildup? Dust and carbon (tar-like dust) are common culprits. Bends, dents, and a burning smell are all bad signs.

Check for Error Codes 

Finally, you can also save time by confirming the potential issue on the dashboard. Most furnaces have a control panel at the front with LED lights and a small screen that displays error codes in case of malfunction. For instance, error code 42 on Carrier furnaces means that you can have an inducer motor problem.

However, even if your furnace doesn’t have similar codes, you may see the LED light blink severally whenever you encounter issues. This light performs the same function. It’s meant to tell you what’s wrong with your furnace.

Count the number of times it blinks between pauses and cross-reference with the chart on the furnace or in your owner’s manual to determine if it means a bad inducer motor.

How to Test a Draft Inducer Motor

Your draft inducer motor is possibly bad if you catch one or more of the seven signs above. But, unfortunately, you can never be too sure.

For instance, a dent on the motor doesn’t necessarily mean that it’s dead. Similarly, an open pressure switch could alternatively mean that the switch is damaged.

So, the next step is to prove beyond doubt that the fan is broken or dead. There are two broad ways to do this;

Conduct a Resistance Test

You can easily test the inducer motor with a multimeter to assess its electrical resistance. All you need is a multimeter. Once you’re ready, turn off the furnace at the breaker, locate the inducer motor, and disconnect the two wires connecting to it. Then set your multimeter to test for resistance (in ohms).

Now, touch each multimeter probe to one of the wires you disconnected and note down the reading. The multimeter should be zero (0) or a value very close to zero. If it’s much higher than zero, it means that the motor is damaged and must be replaced.

Perform a Bypass Test

Many experts don’t recommend bypassing the draft inducer motor– and for a good reason. The critical role of the motor means you’re exposed to grave danger if you bypass it. It leaves you exposed to poisonous gases.

However, you’re allowed to bypass the motor for a few seconds to confirm that it’s the source of your frustrations. To do so, with the furnace switched off at the breaker, disconnect the two wires connecting to the draft inducer switch. Then, holding one wire in each hand, connect them directly and twist.

Now, go back and turn on the heater. Does it run? If so, you now know where the problem lies.

How Much Does It Cost to Replace the Draft Inducer Motor?

The cost to replace the furnace inducer motor ranges from $245 to $465. The actual cost varies depending on many factors, including the type of furnace, type of motor, size, and quality, among others. So, you could pay anything from as little as $85 to as much as $1,200.

Of course, the replacement cost also depends on whether you intend to DIY or hire a professional. Professional service charges start at around $245. This means that you can expect to pay about $245 for a warranty-covered replacement.


Now you know common signs of a bad inducer motor. You even know how to resistance-test a pressure inducer motor using a multimeter and how to bypass the inducer motor if push comes to shove. Just make sure you’re, especially if you decide to test it by bypassing it.