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Serving the Greater New Braunfels, TX Area

Serving the Greater New Braunfels, TX Area


How to Troubleshoot a Failed Furnace


It’s a cold day and your furnace won’t turn on. That’s a big problem, and you’ll want to get it remedied as fast as possible. Fortunately, you can sometimes solve the trouble on your own if you follow several troubleshooting steps.

But, before we get into the main subject of this post, we want to issue a major warning:

Do not attempt to repair your furnace on your own!

The advice we’re giving in this post is how to figure out if there’s a simple error that caused your furnace to stop working. None of these steps involve taking out tools and opening up your furnace’s cabinet to tinker around. Only HVAC professionals have the qualifications, tools, and training to handle actual furnace repairs. Amateur work not only threatens to further damage the furnace, but it’s also potentially hazardous! If following these troubleshooting steps doesn’t get your furnace back to work, just call our team for fast and effective heating repair in San Antonio, TX.

Now, on with the troubleshooting…

Check the power to the furnace

The furnace has its own power switch used to shut it down for the season or in case of safety concerns. It’s located near the furnace cabinet. Check that the switch is set to “on.” If it is, next go to your home’s electrical panel and check on the circuit breaker for the furnace. It may have tripped. (Yes, gas furnaces use electrical power as well.) If you reset the breaker, but the furnace trips it again, call for technicians as this warns of an electrical malfunction with the furnace.

Check the thermostat

This might sound like an obvious step, but people often overlook the basics during an HVAC emergency. If you have a programmable thermostat, check that it hasn’t reverted to a different program. Someone else in the home may have altered the settings without you knowing it. The thermostat may also need new batteries if it isn’t hardwired into the home’s electrical system. 

Make sure the furnace cabinet door is shut

As a safety precaution, most furnaces will not run if their cabinet door is open. Even if the door is loose, the furnace won’t activate. Check this door to see that it’s fully latched shut. 

Change the furnace’s air filter

The air filter, also known as the blower filter, is designed to protect the interior of the furnace from debris coming in through the return air vents. The filter will clog with time, and this will lead to problems with furnace operation. If the filter is dirty enough that it blocks airflow into the furnace, the furnace will overheat and a safety switch will shut the furnace down. Changing out a dirty filter for a clean one may fix the problem. We recommend changing the filter every 1 to 3 months to prevent future problems.

Relight the pilot light (if there is one)

Most furnaces built since 2010 use an electronic ignition system rather than a standing pilot light to ignite the burners. If you have an older furnace with a pilot light, check to see if the pilot has gone out and attempt to relight it if it has. If the pilot won’t stay lit, the furnace probably has a gas flow problem and you’ll need professionals on the job.

At Thayer Air Conditioning, your comfort is our #1 priority! When you need furnace repair, just call us—we’re already on our way!

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