Is your furnace not working? Before you become your own DIY HVAC professional or call in an expert, it will help to know a little about your heating system, how it works, and its functional components. For example, does your furnace have a pilot light? How about a motor and blower? Does your thermostat need batteries to operate?
You can start by reviewing the manual that came with your system. If you don’t have that readily available, you can often find it online at the manufacturer’s site. If all else fails, ask your HVAC professional to give you a guided tour of your system the next time you have your annual safety and efficiency check up. Once you have a good idea of how everything works, use the following six steps to troubleshoot your furnace if it’s not working.
- Does your furnace have power? If you’re not hearing any sounds, like the furnace trying to start or the fan motor running, start by checking your fuse or circuit breaker. Sometimes it’s as easy as a simple reset. If that’s not the problem, check to see if someone accidentally (or kids playing) turned off the furnace at the furnace switch, which is usually found on the side of the unit.
- Is the thermostat calling for heat? Make sure the thermostat is set on the “heat” mode and is set at an appropriate temperature. If in doubt, try turning it up a few more degrees to see if the furnace kicks in. If not, move on to step 3.
- Is the thermostat itself working? If it’s electronic and requires batteries to operate, try a fresh set of batteries. It’s a good maintenance plan to replace thermostat batteries every few months, and especially at the beginning of the heating system. It’s simple, inexpensive, and can avoid an inconvenient shut down.
- Reset the furnace. Most modern furnaces with electronic ignition have a lockout mode if the ignition sequence fails. Given time, they usually reset on their own, but rather than wait, try turning off the furnace, wait a minute, then turn it back on. Lockouts can be caused by electrical brownouts or blackouts or by low gas pressure. If you’ve had any of those conditions, a reset may be all you need. Otherwise, if lockouts continue to occur, you’ll likely need to call in a professional.
- If you have some heat, but not enough. If your furnace is running but shutting off before the house warms up to the set temperature, you may have a dirty filter or something else blocking the airflow. Change or clean your filter and make sure all registers and grilles are open and unblocked.
- Check for outside blockage. High-efficiency furnaces (with plastic venting) can get blocked outside. This is not uncommon in subzero weather. If your vent is where you can get to it safely, take a look to see if it’s blocked with ice, snow, or frost.
If you’ve checked all the above and your furnace is still not running, it’s definitely time to call in your HVAC professional to diagnose and solve the problem.