The blower in your furnace is responsible for moving air throughout your home. So it’s no surprise that if your furnace’s blower is not working, you won’t get any cooling or heating in your home.
There are all sorts of things that will keep a blower from working. Some are due to the blower motor itself. Others are due to furnace components keeping the blower motor from running.
In this article, I’ll go over what you should do when your furnace’s blower won’t turn on. I’ll also go over the different parts that you should check, and how to diagnose common blower motor issues.
What to do when your furnace blower won’t turn on
The first thing that you should do if your furnace blower isn’t turning on is change your thermostat to fan-only mode.
Fan-only mode (also called fan mode) does not heat or cool your home. It only turns the blower on. If your blower doesn’t turn on in fan-only mode, then you’ll need to troubleshoot further.
If you suspect that your thermostat is having issues, then you can bypass your thermostat and test your furnace’s controls directly at the control board.
If you connect the R and G terminals together on your furnace’s control board, that will override the unit to run in fan-only mode.
The last thing to check before proceeding is your furnace’s error code. Your furnace’s control board should have a small indicator light on it. The indicator light will flash in a sequence, depending on the furnace’s status.
For example, if there is an issue with the furnace, then the light will flash in a specific sequence to tell you what is keeping the furnace from running.
If your furnace does not detect any issues, then the light will usually blink on and off in a slow, steady fashion. The specific light blink codes are different for every brand of furnace, so you’ll need to check your owner’s manual for the blink codes for your furnace.
Check the circuit breaker
The next thing that you should do if your furnace’s blower isn’t turning on is to check the circuit breaker.
The furnace’s circuit breaker is a safety device that protects your equipment and wiring from excessive electrical currents.
If your furnace’s circuit breaker trips, go ahead and reset it and see if it runs again.
Keep an eye on your furnace’s startup procedure to see if the breaker trips again at a certain step, depending on what the furnace is doing.
If your furnace’s circuit breaker keeps tripping, then there is an issue with your furnace. Check out my article below for information regarding a furnace that keeps tripping its circuit breaker.
Check the blower motor overload
The motor overload is a device that protects the motor from burning out.
For example, if the blower motor gets stuck, it will start heating up and the motor overload will trip.
When the motor overload trips, power is disconnected from the motor. This helps prevent the motor from burning out or starting a fire.
Most blower motors have a motor overload inside of them to protect them from burning out. The overload can either be automatic or manual reset.
If you have a manual reset motor overload, you’ll see a small red button on the side of your motor. This is the blower motor reset button. The red button pops out when the motor overloads. You’ll need to press the button to reset the overload and get your blower motor running again.
Automatic reset motor overloads don’t have a button on them. Instead, an automatic reset motor overload will reset itself after the motor cools down. You’ll need to wait a while, then the motor overload will reset itself.
Here’s an important tip: If your blower motor’s overload is tripping, then there is an issue with the blower motor. It’s quite possible that there is a mechanical issue with the blower. Are the bearings bad? Is the blower wheel stuck?
If you can’t figure out why your blower motor keeps tripping on overload, then it may be time to call an HVAC professional to check it out.
Check the blower motor capacitor
If you have a PSC (permanent split capacitor) motor, then you should check its capacitor.
The capacitor is needed for the blower motor to start up. Without a capacitor, a PSC blower motor won’t turn on. The capacitor also helps smooth out the rotation of the blower motor once it’s started up.
How do you know if you have a PSC blower motor?
The easiest way to tell if you have a PSC blower motor is to look to see if it has a capacitor. Blower motor capacitors are usually oval in shape and are strapped onto the side of the blower motor.
If the run capacitor is not working, then your blower motor won’t start up.
To test if your run capacitor is working, you’ll need a multimeter.
Check out this video below from AC Service Tech that shows you how to check a furnace blower motor capacitor:
Check the fan belt
Some furnaces (especially older ones) have belt-driven blowers. If the fan belt snaps, your blower motor will spin, but the fan won’t.
So what causes a fan belt to snap? It’s all due to wear and tear.
Even properly installed fan belts eventually wear out, so they are replaceable.
But if your fan belt prematurely wears out, then it’s most likely out of alignment or tension.
One telltale sign of a fan belt that’s out of alignment or tension is a squeaking sound when your furnace is running.
The squeaky noise is coming from the fan belt slipping over the pulley. The fan belt slip is caused by misalignment or incorrect tension.
Check out this video below from AMRE Supply that gives a good overview of how to properly align and tension a blower motor fan belt.