Why Is My Furnace Blower Not Turning On?

If you hear your furnace firing up but the blower never turns on, that’s not normal.

During normal operation, your furnace blower should turn on 1-2 minutes after your burners turn on.

So, what’s the problem? First, let’s rule out a clogged filter. So do this first: check for a dirty air filter and change it if needed

If that didn’t solve the problem, the issue is with one of these 2 components:

  • Your control board/fan switch
  • Your furnace blower 

Let’s take a look at both of these problems to determine whether you can solve the issue yourself or whether you’ll need help from a professional.

Live in the Hastings area and need your furnace blower fixed immediately? Just contact us and we’ll send out a tech right away.

First, turn your fan setting to “ON”

Go to your thermostat and check the fan mode. If it’s set to “AUTO”, switch it to “ON”.

The ON setting forces the fan to blow air constantly instead of just during a heating cycle. So, if you hear the blower motor start, the blower most likely isn’t at fault

Continue on to the next section titled “If your blower starts…” to see what else might be the problem.

Don’t hear the blower motor start? Then skip to the section “If your blower doesn’t start…”

Don’t forget to set your thermostat back to AUTO once you’re done with this step. Here’s an article explaining how keeping your fan set to ON actually wastes a lot of money.

If your blower starts after switching fan to “ON”...

...that means the blower motor is working properly but you most likely have a problem with your control board or fan switch.

To simplify things, here’s an example of the proper communication process that starts your blower motor:

  1. Control board
  2. Fan relay
  3. Fan switch activated
  4. Blower motor starts

But if that communication process breaks down at some point, it means the “START NOW” command never got to the blower motor.

What to do: Have a professional inspect these components to find the issue and repair or replace what’s needed. The good news is that these types of repairs are generally cheaper and easier to fix than replacing a faulty blower motor.

If your blower doesn’t start after switching fan to “ON”...

...that means some component within your blower motor is likely at fault.

3 components that could be faulty include the:

  • Capacitor
  • Belt
  • Blower motor itself

Unfortunately, you’ll need a professional to repair the above components but if you want to save the tech some time, here are some troubleshooting tips that will help you determine which of these components is at fault.

Troubleshooting the capacitor:

Your capacitor is the compact, cylindrical-shaped device that’s attached to the side of the blower motor. 

It acts like a battery and gives the motor the extra surge of energy it needs at start-up. Capacitors, just like batteries, get weak and lose their power over time. And when that happens your blower motor will have trouble turning on.

How to check for faulty capacitor:

  1. Turn the fan back to “ON”. This will trigger the fan switch to start the blower motor. 
  2. Listen for several minutes.
  3. If the capacitor is weak, you’ll hear a loud humming noise for several seconds. Eventually the motor will overheat and shut off until it cools down. After 30 to 60 seconds of cooling down, you’ll hear the loud humming again as the capacitor tries again to start the blower motor.

Troubleshooting the fan belt:

Older furnaces have blower motors that are controlled by a rubber belt. If that belt gets stretched or misaligned, though, the blower won’t turn even if the blower motor is on.

How to check for a faulty fan belt:

  1. Turn off power to furnace. You’ll want to shut off the circuit breaker at the electrical panel that feeds energy to the furnace.
  2. Remove furnace access panel (this may require unscrewing screws with a screwdriver).
  3. Check condition of the belt by visually inspecting it for tears, misalignment, and/or excess slack (there should only be ¾ inches of slack).

Troubleshooting the blower motor:

Sometimes, the reason your blower motor won’t turn on is because the blower motor is old and needs to be replaced. Over time, the motor can wear down from age or lack of lubrication.

How to check for a faulty blower motor:

Turn your fan setting to “ON” and check for a burning smell after several minutes. Note: a faulty blower motor won’t always be accompanied with a burning odor.

Need help from a MN tech?

If you’re still not getting air from your registers, we’re here to help.

Just schedule your appointment and we’ll send over a tech immediately to solve the problem.

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