Why the Burners in Your Furnace Are Not Lighting

Nothing can be more frustrating on a cold winter day than to have your furnace start to heat your home, and then shut off due to the burner losing its flame. Your gas furnace contains a few key components that must all work together in order to keep your home warm and cozy. A furnace cannot be guaranteed to work without malfunctions through its entire service life, although regular maintenance each fall can keep problems to a minimum.

There are a few reasons why a furnace burner will not stay lit, and while you should not attempt to repair a malfunctioning furnace burner on your own, it is helpful to understand why it can happen.


How a Furnace Works

The most common type of furnace is a gas-powered central air system, which heats air in a one area and then distributes it throughout the home via ductwork and vents. Furnaces burn fuel, either natural gas or propane, in order to create heat. The main parts of your furnace are the control system (thermostat and electrical controls), gas valve, burners, heat exchanger, blower, and duct and ventilation system. When your furnace creates heat, combustion gases are vented out of your home via a flue pipe. 

If the burners will not light up, it is because natural gas has not been delivered to the burner for some reason or because safety measures will not allow the burner to become lit. If the ignition process fails, it may be due to the thermocouple or flame sensor. It could also point to a few other problems as well, so you should always trust heating repair to a trained technician who knows the proper safety procedures and can quickly identify the issue.


Reasons Your Burner Won’t Stay Lit


  • The Furnace is Turned Off

If this is the first time you have tried to turn on your furnace for the season and the burners are not coming on, the reason may be that you forgot to turn on the furnace switch. It is usually located next to the furnace.


  • The Pilot Light is Out

Newer furnaces no longer use standing pilot lights to ignite the burners, but you may have an older model that does use a pilot light. Check to see if it has gone out. If it has, you will need to relight it. If it keeps going out, there may be an issue with the gas line or the pilot assembly needs cleaning. Call an HVAC professional to check it out.


  • A Circuit Breaker Has Tripped

Gas furnaces do not run exclusively on natural gas power. Modern furnaces use electronic ignition systems to light up the burners, either directly with a hot surface igniter, or indirectly with an intermittent pilot light. If the blower motor in the furnace causes a power overload that trips the circuit breaker, not only will the motor fail to come on, the burners will not ignite either. Check the electrical panel to see if there is a tripped breaker and reset it. If the furnace continues to overload the circuit, call an HVAC professional to check it out.


  • Broken Electric Ignition System

Your furnace probably uses an electronic ignition system to light the burners, usually by heating up its surface similar to a lightbulb. Like any electrical component, the igniter for a furnace can break. This is probably the most common malfunction in gas furnaces. It could be an electrical failure, such as with the control board or bad wiring, or the igniter may have cracked. Do not try to tamper with the igniter on your own: a professional can diagnose what is wrong and then have the igniter replaced. This is an easy and fast job for an experienced HVAC technician, and the furnace will be back to working shape in no time.


  • Broken Thermocouple

A thermocouple is a safety component that uses two different types of metal wire to measure the temperature of the flame. This is so it can manage the gas flow to the burner. When the thermocouple senses that the flame is not hot enough, it shuts off the flow of gas so that your home is not filled with dangerous flammable gas. If the thermocouple malfunctions, it can incorrectly shut off the gas, which your furnace will not stay lit.


  • Dirty Flame Sensor

Modern furnaces actually use a flame sensor instead of a thermocouple because modern furnaces most often use hot surface ignition to ignite the burners. This eliminates the need for a pilot light, as the flame sensor simply detects when gas has been ignited and shuts off the igniter afterwards. This part is hindered by any dust, and may need an expert to safely clean it from time to time, perhaps during annual heating maintenance.


  • The Burners are Dirty

A layer of grime across the burners cuts off the supply of oxygen necessary for the burners to light. Please do not attempt to clean the burners yourself; our team of furnace technicians can safely remove the burners and clean them.


  • Thermostat Has Lost Connection

The issue may be in the thermostat itself, not in the furnace unit. The thermostat’s connection to the igniter may have failed, or it is not sensing temperatures correctly and therefore will not ignite the burners.


  • Gas Line Issues

Gas may not be flowing to the burners. If this is the first time you have used the furnace in months, you may have forgotten to open the gas valve to the furnace. If the burners still will not ignite, close the gas valve and call us for assistance. You do not want to tamper with the gas line!



Final Thoughts

As cold weather approaches, it is important to take a few preventative measures to protect your home through the chilly months. Whether your pilot light will not stay lit or you think your furnace may not be running optimally, you can always count on the Aire-Tech to keep your home warm. Perhaps you need repairs, new furnace installation, or preventative maintenance—whatever the HVAC issue is, Aire-Tech is ready to help.

If your system needs repair or inspection before winter, call us on 951-926-1002. You can also visit our Contact page and complete the contact form.