Your furnace's burners serve a fairly critical function—they distribute the gas that your furnace ultimately burns to provide heat for your home. Most furnaces contain a single burner unit, but some units usually have multiple individual burner tubes. A typical design includes a manifold that distributes gas to each burner to provide clean and even heat.

Burner units are relatively simple components, but they can still suffer from several potential failures. Since your furnace likely has multiple burners, these failures may not stop your furnace from lighting entirely. Understanding why these problems happen can save you from replacing your furnace's entire burner assembly.

What Are Partial Burner Failures?

A partial burner failure occurs when one or more individual burners in your furnace fails to light or fails to produce a clean, even burn. You can check the flames on your furnace by carefully observing the burners with the door removed. If everything is working as it should, you'll see a bright blue flame from each burner tube.

On the other hand, a partial failure may present itself in several ways. For example, you may notice that only some of your burners ignite. In this case, the limit switch may never detect a high enough temperature, causing your furnace to shut down or the blower to remain off. You may also notice that some of the burners produce uneven or red-yellow flames, indicating dirty or inefficient burns.

Note that an inefficiently operating furnace may still run and produce heat, but you should avoid using it. Yellow or red flames typically mean that your furnace isn't receiving enough oxygen for complete combustion. This condition can generate soot which will clog your burners and cause even more problems in the future, and you may also be generating higher levels of dangerous CO2.

How Can You Repair Partial Failures?

If you notice a partial failure with your burner, there's a good chance you'll need to clean or replace one or more of your burners. Cleaning the burner is usually a good first step since built-up soot or other debris can create a clog that may prevent complete combustion or ignition. If you're handy, you can usually find instructions to try cleaning the burners yourself.

However, when cleaning doesn't resolve the issue, you'll usually need to replace the burners or burner assembly. Depending on the model of your furnace, you may be able to replace only the faulty burners, or you may have to replace the whole unit. In either case, it's critical to perform this repair before using your furnace again to avoid causing more damage or creating dangerous fumes.

For more information on furnace repair, contact a professional near you.