Top 10 Reasons Your Furnace Isn’t Working and What To Do Next

Furnaces are a critical part of the heating system in any home, and not working properly can be a big problem. When you don’t have heat at home, it can feel like the coldest time of the year. Before you give up, read through this article to get some ideas on how to troubleshoot your furnace and get it working again. In general, furnaces should last for 10 to 15 years if they’re cared for properly. Regular maintenance, as well as correct installation, will help extend the lifespan of your furnace. However, no matter how well-cared-for it is, sooner or later every furnace will need attention from an expert. Any sign that your furnace might be malfunctioning should prompt you to take action right away. If you ignore small issues now, they may become much bigger problems soon enough. Read these top 10 reasons your furnace isn’t working with tips on what to do next:

Your Furnace Has a Leak

If you notice a drop in energy efficiency, this could be an indication that your furnace has a small leak in the system that is allowing hot gas to escape. A drop in efficiency can also be caused by an accumulation of dust or debris in the blower motor that’s causing friction, which leads to an increased energy draw. To determine if the drop in efficiency is due to a leak, you can do a simple visual inspection and/or use a leak detection spray. To solve the problem, you can turn off your furnace and remove the blower cover. Follow the gas line to find the leak and then apply some pipe sealant to the leak. If you have a furnace that uses a seal-type heating element, you may be able to solve the problem by simply replacing the gasket. If the leak is coming from the burner or gas valve, you’ll need to replace these pieces.

There’s Dirty Ductwork

If your furnace isn’t working as well as it once did, but everything else appears to be in working condition, the issue may be dirty ductwork. As air passes through the ductwork, it picks up dust and dirt. This dirt can clog the system, reducing airflow and causing the furnace to work harder and burn more fuel. Dirty ductwork is often caused by having too many bends and turns in the ductwork, which can be corrected by installing a duct reel. You can also install a duct cleaning device, or hire a contractor to do the cleaning. Make sure you do it at least once a year.

Your Furnace Has an Incorrect Thermostat

If your furnace isn’t firing up when it should or is coming on and off at odd times, the problem may be a faulty or improperly-installed thermostat. A thermostat should respond to changes in temperature and be able to recognize what the desired temperature inside your home is. To troubleshoot an incorrectly installed or faulty thermostat, you can turn off the furnace, open up the wall panel, and then use a voltage tester to determine if the thermostat is receiving power. If it is not receiving power, the problem is likely related to incorrect wiring or a blown fuse. If it is receiving power but not switching the furnace on, you can try resetting the thermostat by unplugging it and then plugging it back in.

Your Funeral Has a Dirty Filter

If your furnace isn’t working as efficiently as it once did, dirty or clogged filters may be the problem. You should replace or clean your furnace filter every 30 to 60 days, depending on where you live and the air quality in your home. Dirty or clogged filters will reduce airflow and put additional strain on the furnace, causing it to work harder and use more fuel to heat your home. If your filter is clogged or dirty, simply remove it, clean it, and then put it back in place. Some filters are washable, but many need to be replaced every year. If you can’t tell if your filter is clogged, tap it lightly against a hard surface to dislodge any debris.

You Don’t Have the Right Size Furnace

If you’ve recently installed a new furnace, it’s possible that you didn’t account for the difference in BTU output between the old and new systems. If the new furnace is putting out more BTU than the entire system is designed to handle, there could be a problem. If you’ve just installed a new furnace and your system isn’t working correctly, you may have the wrong size furnace. So, before you call in a technician, you should double-check the BTU output of your new furnace. If you have the correct furnace for the home, but the system is still not working correctly, there may be another problem.

There is Incorrect Voltage Going to the Furnace

If your furnace isn’t working at all, the problem could be related to the voltage going to it. You may have the wrong voltage going to your furnace, or there may be a problem with the wiring. To troubleshoot this issue, you can shut off the power to the furnace at the circuit breaker and then use a voltage tester to determine if the voltage going to your furnace is correct. If it is not correct, you can call an electrician to correct the wiring.

One or More of your Furnace Burners Doesn’t Work

If one or more of the burners on your furnace is not working, the problem could be related to a few different things. The faulty burner may need to be replaced, or there could be a problem with the gas supply. If one of the burners isn’t working, you can test it by turning off the furnace and then disconnecting the gas supply to that burner. You can then use a match or long-stemmed lighter to see if the pilot light is still burning. If it is, you can try to reset the pilot. If it isn’t, you’ll need to replace the burner. If there is a problem with the gas supply, you may need to call an expert to fix it.


Furnaces are an essential part of any home, but they do fail from time to time. This article has explored the 10 most common reasons why a furnace may be malfunctioning, along with tips on what to do next. To ensure your furnace is running at peak performance all year round, you should schedule furnace maintenance with a local HVAC contractor at least once a year.