What is a Furnace Light Code and How to Fix It

It can be easy to take your furnace for granted when you are in the middle of a drafty winter. After all, when it’s freezing outside, and you are shivering inside, it is easy to forget that there is a complex heating system designed to keep your home warm and comfortable under all that insulation and wall panelling. But as any experienced homeowner knows, things don’t always go according to plan—especially if you have a code-deficient furnace. If your furnace light code keeps coming on, it could signify that something is amiss with your HVAC system. Fortunately, diagnosing and correcting this problem can be fairly straightforward. Whether you need help troubleshooting or want some advice about what to look out for before contacting a professional, read on to learn more…

What is a Furnace Light Code?

A furnace light code is an error code that appears on your furnace’s digital display when there is a problem with your system. If you have a furnace light code, there is a short-term problem with your HVAC system. A light code can be caused by several issues, including air duct blockages, debris on the burner, or malfunctioning electronic controls. The good news is that most furnace light codes are very easy to troubleshoot. In most cases, you need to correct the underlying problem, and the light code will go away. There are a few serious issues that can cause a light code, but these are easy to correct for the most part.

Check Your Vents

Furnace light codes can also indicate that something is blocking your vents. Ensure that furniture, carpets, or curtains do not block your air vents. If you have an indoor-air-quality issue, such as a bad smell or dust buildup, you can use a HEPA filter to catch it all. If you have a furnace light code and blocked vents, you will have to temporarily unblock the vents until you can have your furnace repaired. Otherwise, your furnace will turn off completely. The problem with an unrepaired furnace is that it can quickly grow more serious, leading to major furnace repairs. Dust and debris can clog up your furnace vents, causing them to get too hot. If your vents are blocked, then your furnace will not be able to get fresh air, which will cause your furnace to overheat. Furnace vents that are blocked or clogged can also cause your furnace to sound like a jet engine.

You Have a Blockage

Sometimes a furnace light code means you have a blockage in your system. This is often caused by a buildup of ash from your burners. If you are using a gas furnace, you will want to regularly clean out the ashes from your furnace to prevent a buildup. This can cause your furnace to malfunction and trigger a light code. You can also take steps to prevent a blockage from occurring in the first place. While cleaning out your furnace, you can also vacuum out the dust and debris that has built up in your indoor air ducts. This can help keep your furnace running smoothly. Another cause of a blockage could be a problem with the ductwork. If you have recently made any changes to your ductwork, make sure to correct the problem before it causes a furnace light code.

Your Burner Orings Are Shrinking

If you have a furnace light code and use a gas furnace, you may have a problem with your burner rings. Orings are the rubber rings that fit around your burners and help seal off your furnace. As these rings get older, they can shrink, which can cause your furnace to misfire. To rectify this problem, you will need to replace your burner rings. Replacing your burner rings is a relatively easy repair that can be completed in your garage or basement. If you have a major problem with your furnace, it is good to have a professional come out and look at it. Otherwise, you can easily resolve this issue yourself. While looking at your rings, you may want to also look at your blower wheel. A faulty blower wheel can also cause your furnace to misfire.

Your Electronic Controls Are Malfunctioning

Faulty electronic controls can also cause a furnace light code. This is a more serious issue that should be inspected by a professional. If you have a furnace light code caused by a problem with your controls, you will need to hire a professional to repair it. While replacing a few parts yourself is possible, it is significantly more difficult than replacing a few rings. If you have a furnace light code caused by a problem with your controls, it is best to have a professional come out and repair them. This is because they are very difficult to fix on your own. Several common issues can cause your electronic controls to malfunction, including a blown a fuse or a loose connection. If you notice a furnace light code and believe a problem with your electronic controls may cause it, you should have your furnace inspected by a professional.


If you have a furnace light code, it is important not to ignore it. A furnace light code indicates a serious problem with your HVAC system. In most cases, fixing the underlying issue will resolve the code. However, some issues can cause a light code and require more significant repairs. Even if you do not know what is causing the problem, you should have your furnace inspected by a professional. A furnace light code can lead to more serious problems, such as a fire. In most cases, the problem is easily and inexpensively fixed. However, it is important to address it as soon as possible to prevent the problem from growing worse.