Tips & Resources
Regular maintenance goes a long way toward ensuring that your furnace functions properly all winter long. However, problems can still occur. Before calling for a repair, here are 10 simple furnace troubleshooting tips you can check and potentially fix yourself. From the filter to the thermostat, some basic knowledge might save you some money and get your furnace working again quickly.
Furnace filters get clogged with dirt, dust and debris over time. This impedes the airflow necessary to keep your system running smoothly and efficiently. Lack of sufficient airflow can prevent the furnace from turning on and eventually that buildup can even become a fire hazard. Check the filter every 30 days by holding it up to a light source. If no or minimal light passes through, clean or replace it immediately. Filters need to be replaced every 30 to 90 days or according to the manufacturer’s recommendations.
Switches can inadvertently be turned off. If that is the case, simply flip the switch back on. If that is not the issue, check that power is turned on at the breaker box or fuse box.
Make sure the HVAC breaker is on. If the breakers aren’t labeled, look for one that is in the opposite position of the rest. To reset the breaker, flip the switch all the way off and then back on. If you have a fuse box, look for the fuse that is melted or discolored. Replace it with the same size fuse. Turn the furnace switch on to see if power is restored to the furnace.
Furnaces manufactured after 1990 have a small window that flashes a light in a certain sequence. That code corresponds to a specific problem. Flip the furnace switch off and back on and note the sequence of the flashing light. A key that shows the meaning of the code can be found inside one of the access panel doors. This may not be an issue you can correct, but it is useful information to provide to your HVAC technician.
A healthy furnace flame is blue and may have a yellowish tip. This indicates that the fuel is burning safely and efficiently. A flame that is any other color (red, yellow, purple, green) indicates a problem that should be addressed by a professional right away.
If the flame is out completely, it needs to be relit. Turn off the gas for 10 to 15 minutes prior to relighting. Consult your owner’s manual and follow the instructions. Do not proceed if there is any lingering gas smell. That smell could indicate a leak. In that case, follow standard safety precautions — evacuate the home and call the gas company and fire department from a safe distance.
Many furnaces will not operate if the front panel is not completely closed.
Blocked vents and registers affect comfort and can result in duct leaks as well as HVAC breakdowns. All vents and registers should be fully open and unblocked, even those in unused rooms. Remove anything that is restricting airflow, such as rugs, furniture or other objects.
Make sure the thermostat is set to “heat.” Test it by setting the temperature 5 or more degrees higher than the current room temperature. This should trigger the furnace to turn on. If it doesn’t, check the batteries and replace them if necessary. Electromechanical thermostats may need a gentle dusting with a soft brush on the inside. Make sure your thermostat is located properly, away from sunlight, lamps or other heat sources or drafts.
Annual maintenance is the best way to ensure that your furnace will run properly and efficiently throughout the winter. Schedule your maintenance appointment before the cold weather hits when technicians are not as busy. Proper maintenance saves money and inconvenience over the life of the furnace and is even required by some manufacturers to keep the warranty in force.