What Causes Your Outdoor Furnace Blower Fan to Fail?

What Causes Your Outdoor Furnace Blower Fan to Fail?

All outdoor wood boilers are designed to outlast their electronics so these parts WILL fail due to normal wear and tear. It could fail during the normal operation of your outdoor wood furnace. They run continuously and you just never know WHEN they will fail - it could be Christmas morning!

Blower fans, one of the essential electronics of an outdoor wood stove, don't usually just go from NORMAL to DEAD instantly. They often die slowly and if you pay attention, you can be prepared for this.

Also, please remember to use the correct size of the blower fan.

Here are some possible causes why your blower fan fails sooner than expected.

  • Age and general wear. Over time, components of the blower fan may wear out naturally, leading to decreased efficiency and eventual failure. As mentioned above, your outdoor wood stove will last longer than its electronics and other parts so you need to replace them.
  • Maintenance. Poor maintenance can cause an accumulation of dirt, dust, and debris on the blower fan, which can make it difficult for it to function. This accumulation over time may put stress on the motor, restrict airflow, and lead to fan failure.
  • Overfiring or frequent overheating. If your outdoor wood burner overheats, it can damage the furnace and its component. If your motor’s electrics and bearings are constantly exposed to too much heat, then they will begin to fail. Read our article “Has Your Outdoor Furnace Overheated?” to evaluate the most common reasons for furnace overheating. A minor issue can quickly turn into something far worse.
  • Electrical Issues. The blower fan might stop working if there are faults with the electrical wiring, switches, or control panel. This could be caused by faulty electrical parts, blown fuses, tripped circuit breakers, or weak connections.
  • Environmental factors. Extreme weather conditions, such as exposure to excessive moisture, extreme temperatures, or corrosive elements, can affect the performance and longevity of the blower fan.

An electronic component could also fail when the temps are below zero and other (much more expensive) components will freeze and be destroyed before spare parts arrive! Do NOT risk freeze damage!

The Blower Fan Won’t Turn On

Are you trying to determine why your furnace blower won’t turn on? Check the High limit switch. The high-limit switch is a safety switch that ALL outdoor wood furnaces should have. This little device will cut the power to your blower fan if the furnace is overheating.

Read our article “Outdoor Furnace: High Limit Safety Switch Basics” for more information about the high limit switch.

We are getting calls from many customers whose outdoor wood boiler blower fans are NEAR DEATH, but they don't realize this. A blower fan that is near death should be replaced immediately!

Here are the TOP 4 Signs Your Blower is Near Death:

1. You see an increase in CREOSOTE in your outdoor wood boiler. This is a sign of poor combustion, likely from a failing blower.

Click HERE for our Creosote Remover Stick that can help creosote build-up easier to remove.

2. You feel little or no air from the fan. Place your hand in front of the airflow opening (door) and feel the airflow. The airflow should be sufficient to blow your hair away from your face (if you have hair!).
Burn Caution: If the airflow opening on your boiler is inside the boiler, do not use your hand, but rather attach a 5" strip of plastic (from a grocery bag) to a stick and hold it in front of the airflow.

3. Unusual Fan Noise/High Amperage. A failing fan will often make a humming sound or a squealing sound. If the fan is not spinning, sometimes it can be started spinning and it takes off. (Do not use your hand to start it!) If a routine check of the amperage load to the motor reveals high amperage, the motor is working too hard and will fail soon. This test is done using an amp meter on the common wire.

4. Wood Not Burning Well. If your wood is not burning well, this is usually a sign of poor airflow. Airflow problems can be caused by a bad solenoid, a blockage of some sort, or because your blower fan is NEAR DEATH! Click HERE for a replacement solenoid.

Again, a blower fan that is near death should be replaced immediately! A blower fan cannot be oiled - they are designed to be maintenance-free, and then just replaced when they reach their end of life. The lowest cost maintenance is a full replacement - components of the fan are not available to replace cost-effectively.


Since all outdoor wood burners are designed to OUTLAST their electronics, we recommend that you always have a SPARE of the four main electrical components:

1. Blower Fan
2. Boiler Pump
3. Wood boiler Solenoid
4. High Limit Safety Switch
We call these four items the "Emergency Prep Kit".



It is important to note that the cause of blower fan failure may vary. If you experience problems with your outdoor furnace blower fan, call our office at 231-861-8200 for an accurate diagnosis and correct replacement if you need it. We send money-saving tips and maintenance reminders that help you maximize the life span and efficiency of your outdoor boiler. For more outdoor wood boiler parts, visit our online store OutdoorBoiler.com!