When your furnace won’t stay lit, contact a certified technician to get it working. That’s the easiest and safest way to address the issue. Nonetheless, a burner that won’t stay lit is one of the more common issues you may run into, so it helps to understand why.
As the go-to contractor for furnace repair in Carmel, IN, our certified crew at Comfort Heating, Air & Plumbing can help you figure out why your furnace won’t stay lit.
Faulty Flame Sensor
The flame sensor acts as a safety precaution in gas furnaces that tests if the gas coming from the burners has ignited. If the sensor doesn’t detect flames or feel the pilot light, it automatically shuts off gas flow to prevent the combustion chamber from flooding with unburned gas.
If the gas valve opens when the furnace is not lit, toxic gas could build up and potentially cause a fire or explosion.
If the flame sensor malfunctions, it mistakenly senses that the burners have ignited and shuts off the gas supply, causing the burners to go out. Flame sensors need regular cleaning, maintenance, and occasional replacement.
Incorrectly Positioned Flame Sensor
Many furnaces have the flame sensor very close to or actively touching the pilot light. If the flame sensor is out of position, it assumes you have an unlit pilot light and shuts off the gas. An incorrectly positioned flame sensor may require repositioning or replacing.
Insufficient Airflow to the Furnace
Burners need constant airflow (typically drawn by the blower fan from their return air ducts) to ignite. However, if a faulty blower or clogged furnace filter chokes off airflow, the burners won’t stay on for long. While you can change the furnace filter yourself, a faulty blower needs professional repairs.
An Overheating Heat Exchanger
Your furnace won’t stay lit when the heat exchanger overheats because that activates the limit switch. The limit switch, acting as a safety feature, then shuts off the gas supply and power to the furnace. A clogged filter may also restrict airflow around the heat exchanger, causing it to overheat.
The heat exchanger could also overheat if the furnace fails to properly vent out combustion gas — an issue you want experts to fix as soon as possible.
Faulty Control Board
The control board regulates when other furnace components turn on and off. If you have a faulty control board, it can cause burners to shut off after a short time. A seasoned professional can examine the control board to see if they can fix or replace it.
Faulty Limit Switch
Occasionally, the limit switch may simply break and require replacing. It may trigger a false signal of the furnace overheating, prompting the burners to shut down as a precaution.
Malfunctioning Thermostat
Regardless of what you set it to, a faulty thermostat may send the wrong signals to your furnace. As a result, the furnace may not know when to light. Your local HVAC professional may be able to fix a bad thermostat, but you may have to replace it.
Dirty Flame Sensor
If your furnace turns on several times and turns back off within a few seconds, you probably have a dirty flame sensor. Rather than try to clean the sensor yourself, schedule service with an experienced professional.
As a safety measure, you may want to install a flame sensor designed to turn off the gas valve as soon as it detects no flame.
Dirt on the Burners
Flames from the burners may go out when they struggle to draw sufficient oxygen for combustion through excess dirt and grime along the surface. This often occurs with furnaces that receive poor maintenance.
Schedule an HVAC inspection to determine if your burners need cleaning. However, don’t try to clean the burners yourself since the job requires you to detach the burner assembly first.
Turn to Complete Comfort Heating, A/C & Plumbing Repair for Your Furnace Needs
Now that you know why your furnace won’t stay lit, you want to hire a competent expert to troubleshoot, diagnose, and fix your unit. Trust our certified technicians at Complete Comfort Heating, A/C & Plumbing Repair to restore your furnace to proper working condition.
As a highly trained and EPA-certified team, we stay committed to making you as comfortable as possible and never charge for after-hours service. Call Complete Comfort Heating, A/C & Plumbing Repair at (317) 759-2529 to schedule service in Greenwood, IN, or nearby areas.
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