A common customer experience for homeowners is dealing with furnace lockout. Furnaces have an inbuilt sensor that detects potential problems or safety issues. When a problem triggers the sensor, the furnace will activate a kill switch to the power, causing a furnace lockout.

There are many reasons why a furnace stops working. It can be frustrating to diagnose, but sometimes, it is a simple fix! Discover why your furnace isn’t working correctly with the five most common causes of furnace lockout. 

5 Common Causes of Furnace Lockout 

A Dirty Flame Sensor

The most common furnace problem is a dirty flame sensor. A flame sensor is an inbuilt feature in most modern gas furnaces that ensures the gas valve opens only while the flames are burning. This prevents gas leaks or fires. And while it is a great safety feature of furnaces, too much carbon build-up on the sensor can obscure its ability to detect a flame. 

A tell-tale sign that your flame sensor is dirty is when you try to turn on your furnace, and the igniter lights a flame, but within a few seconds, the flame goes out. Furnaces typically try three to five times to light the flame before it triggers a furnace lockout. A furnace lockout can last up to three hours, and in that time, the furnace will not turn on or restart. 

A Dirty Air Filter 

A dirty air filter is one of the main reasons your furnace could be overheating. Without proper airflow, your furnace will work harder to get air, causing it to overheat. A dirty furnace filter will affect your furnace’s performance. Most furnaces have a high-limit switch which looks like a black cylinder box. The high-limit switch turns the furnace off automatically if the furnace reaches a specific temperature. As a homeowner, you can easily replace the furnace filter or call an HVAC technician if you are uncomfortable doing this. 

A Bad Inducer Motor 

An inducer motor is a motorized fan that moves air through the furnace and heating vents. Most inducer motors fail due to an aging furnace. However, inducer motors can also become clogged by debris. Diagnosing inducer motor problems can be challenging without experience. If you suspect a bad inducer motor is causing your furnace lockout, we recommend calling an experienced HVAC technician to service your furnace

A Failing Blower Motor

A blower motor takes heated and cooled air from the furnace and circulates it throughout your home. A common sign of a blower motor failing is a burnt plastic smell throughout your home. Other signs are low airflow from your furnace, no airflow, or strange noises within the first few minutes of starting your furnace. A sudden, unexplainable increase in your energy bill with similar usage habits can indicate a failing blower motor. 

A Malfunctioning Control Board 

The control board acts as the brain of your furnace. If your control board malfunctions, it will cause various problems. Lack of power to the blower motor or the igniter is one sign. Another is the air conditioner and the furnace turning on simultaneously. 

Diagnosing how to fix furnace lockout caused by a control board issue requires extensive electrical and mechanical knowledge. Therefore, this furnace lockout problem is best suited for a trained HVAC technician.  

How to Fix Furnace Lockout Caused By Something Else

We recommend calling an expert for any other common furnace problems not mentioned. Furnaces are crucial to your home’s safety and air quality, and if you are experiencing problems, it’s best to fix them immediately. A trained HVAC service technician can run various tests on your furnace while inspecting it for safety, energy efficiency, and performance. 

Get Annual Furnace Maintenance With Bend Heating

If you haven’t found your solution for how to fix furnace lockout, maybe it’s time to call an expert. Bend Heating & Sheet Metal offers yearly maintenance programs for furnaces, air conditioners, heat pumps, and other HVAC systems. 

Anticipate any future furnace problems now with a preventative maintenance package. This includes a prescheduled maintenance appointment each year and priority 24/7 service repairs (so you won’t have to wait in line when you need us). 

Get discounts on the costs of maintenance and repairs, and be proactive about your furnace problem. Call us at 541-382-1231 or check out our maintenance page for more information on furnace repairs.