When the Solenoid Fails: Understanding the Effect on Your Outdoor Wood Boiler

When the Solenoid Fails: Understanding the Effect on Your Outdoor Wood Boiler

What happens when the solenoid fails? When to determine to buy a new one?

The wood boiler solenoid is the device that when energized, becomes a magnet that lifts the damper plate that allows air to flow from the outdoor wood boiler blower fan into the boiler. If it is failing, this is easy to diagnose - just remove the cover and turn the fan switch on and off to see if the solenoid is lifting the damper plate.

Outdoor Boiler Solenoid

In this article, we'll discuss what happens when the solenoid on your outdoor wood furnace fails and what impact it could have on your heating system.

What Causes the Solenoid to Fail?

Here are some possible causes why a solenoid would fail:

  1. Mechanical Wear and Tear. A solenoid's mechanical parts are subject to wear and tear over time. Continuous use, exposure to severe weather, or poor maintenance can cause essential components, like the valve or seals, to deteriorate, which will result in the solenoid failing.
  2. Blockage. Remember, that outdoor wood-burning boilers operate in environments where dirt, debris, and unwanted substances may enter the system. These particles may clog passageways or obstruct valve action if they get within the solenoid, which could result in failure or malfunction.
  3. Rust and Corrosion. The moisture that outdoor wood-burning boilers are subjected to might cause the solenoid components to corrode and rust. The solenoid valve may become inoperable as a result of corrosion, which may affect its operation and movement.
  4. Maintenance. Failures of solenoids can be attributed to poor maintenance. The durability and dependability of the solenoid might be affected by improperly fastened connections, incorrect voltage levels, insufficient lubrication, skipping routine checks, and other factors.
  5. Overheating. The interior parts of a solenoid could be damaged by excessive heat. The insulation or wire inside the solenoid may deteriorate and fail if it is exposed to high temperatures as a result of frequent furnace overheating.

What Happens When the Solenoid Fails?

  1. Loss of Heat and Inefficient Heat Transfer. The solenoid lifts the damper plate which allows air to flow from the fan into the boiler. A failed solenoid can disrupt this airflow, resulting in a lack of heat and hot water throughout your system. The water jacket temp stays low and the temp NEVER gets up to the max temperature. This can lead to inefficient transfer and your home may struggle to reach the desired temperature.
  2. Overheating and Potential Damage. One of the potential reasons for overheating is when your solenoid is stuck open. This happens when the solenoid lifts the damper and it gets stuck and does not go down. This will allow continuous airflow and could make the blower fan to continuously run. This will cause the high-limit switch to trip. If you don’t have a snap disc high-limit switch, the temperature will continue to go up.

Read our blog article “Outdoor Furnace: High Limit Safety Switch Is Tripping” for more information about this topic.

We recommend that all outdoor wood burner owners have an extra high-limit switch on hand and available. No furnace can be operated without one.



It's important to check the boiler's power source before concluding the solenoid has failed. To troubleshoot power-related issues, take these steps:

  • Power source. Check whether the outdoor wood boiler's electrical supply is in good working order.
  • Wiring connections. Inspect the solenoid's wire connections. Check for disconnected or loose wires. Carefully tighten any loose connections or reattach any detached wires.
  • Lubricate. It is recommended to lubricate or grease the solenoid regularly. If the wirings are all working properly, check if the solenoid is stuck open. This happens when the solenoid lifts the damper and it does not go down. A stuck solenoid allows air leak, wherein, the air will continuously flow from the blower fan which could make the temperature keep on going up. This will make the high-limit switch trip and if you don’t have a high-limit switch, it could cause overheating.

When to Replace The Solenoid?

Once the power source has been confirmed to be working properly, then it’s time to check on the solenoid itself. Look for any physical damage, rust, or loose parts on the solenoid. Inspect the solenoid's wiring connections for any evidence of wear or damage. If all other troubleshooting steps have failed and the solenoid appears to be defective, then it's time for a replacement. Make sure to buy a compatible replacement or, if necessary, get in touch with a trained technician. Click HERE to order a replacement.


Although a broken solenoid in your outdoor wood furnace can be frustrating, you can efficiently diagnose and fix the problem by using the troubleshooting techniques above. Don't forget to get professional assistance if necessary. Quick action will guarantee a warm and cozy atmosphere during the colder months.

Contact OutdoorBoiler.com for any questions. Our dedicated team is trained and experienced in all things outdoor wood boiler. You can always expect a human on the other end of the line. We know what’s important to you - your family, saving money, and keeping your house toasty warm - and we make that our highest priority.