Every modern furnace is equipped with a safety reset button that shuts the system down in the event of a malfunction. This reset button is an important indication of a problem with your furnace, so you should be attentive to it. While it's not uncommon for a furnace to trip the reset button on a rare occasion as a glitch, if your furnace is tripping it repeatedly, that's a unit that's trying to tell you something. Here's a look at some of the most common problems that lead to furnace reset button tripping.
Air Filter Problems
Your furnace depends on sufficient airflow to maintain the balance of the temperature within the firebox and the proper airflow beyond the blower fan. When you don't keep your air filters changed or cleaned the way that you should, this leads to insufficient air supply in the furnace, which often trips the reset button because the furnace can't perform the way that it should. Check the furnace filter first when the reset button trips because it's the easiest and most cost-effective problem to resolve.
Fuel Supply Disruption
Whether you've run out of fuel or your fuel supply line is clogged, a disruption in the fuel supply to your furnace will typically trip the reset button because the pilot light will go out. When the pilot light goes out, the flame sensor triggers the safety button to prevent fuel from accumulating in the house. Check your fuel tank for adequate fuel supply and ensure that the lines are clear before resetting the system.
Whether it's due to a blower fan malfunction or a thermostat problem, excess heat inside the firebox will cause your furnace to trip the high-limit switch. This switch will trigger the reset button to shut the furnace down in an effort to prevent a fire. You'll need to have the thermostat tested and check the blower fan to see if there's a malfunction somewhere in the system to resolve this.
Dirty Flame Sensor
When the flame sensor gets dirty, it doesn't always read the presence of the flame correctly. Sometimes, the dirt can even cause the flame sensor to send intermittent and unpredictable signals back to the safety switch. You'll want to make sure that you keep the flame sensor clean and double-check the connections periodically to ensure that your furnace doesn't suffer needless disruption simply due to soot and other types of buildup on the sensor.
These are some of the most common reasons why your home furnace might trip the safety button. Talk with a heating services technician for more help.