If your furnace won't turn on and you've checked the power source and thermostat, one thing you might want to consider is that the furnace shut itself down as a safety precaution. This can happen when the flame sensor is bad. Here are signs of a bad flame sensor and how a furnace repair technician can fix the problem.
Signs The Flame Sensor In Your Furnace Is Bad
The flame sensor is a part that plays an important safety role in your furnace. It detects that the gas has ignited the burners. If flame is not detected, then the sensor shuts down the gas to prevent a gas leak. So, if your furnace turns on and then kicks back off several seconds later, you should suspect a safety shutdown. Your furnace may allow this to happen a few times in succession before shutting down the furnace for good.
Your furnace repair professional will check the sensor to see if it is cracked or dirty. The sensor is behind the panel and mounted outside of the burner assembly, but the furnace technician can pull the sensor out to look at it. When it's dirty, it will be black from carbon buildup, and if it's damaged, a crack will usually be visible in the porcelain portion of the sensor.
Furnace Repairs That Might Be Needed
There are two ways to fix a problem with the ignition sensor. The technician can clean it or replace it. Cleaning requires scrubbing the sensor with an emery cloth to get rid of the carbon. When the sensor is clean, it can then be reinstalled and tested. If the sensor is cracked, it will have to be replaced with a new sensor. Also, if the furnace doesn't work after cleaning the sensor, the technician may put in a new sensor even if a crack can't be seen just to see if that fixes the problem.
You might be able to prevent the need for this type of furnace repair by having an annual service call that maintains your furnace. The service call usually includes cleaning the buildup off of the sensor, and that might prevent a breakdown of the furnace. However, a crack could happen at any time, so if your furnace won't start and you can't figure out why, call an HVAC repair company to check the ignition sensor to see if that's the problem.
Other things can cause your furnace to break down, so the sensor may not be to blame. If you don't feel comfortable taking the panel off of your furnace to check the sensor, then let the technician do it for you and determine if the sensor is the culprit or if something else is wrong with your furnace.