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Furnace Main Burner Shuts Off After Ignition: 4 Reasons Why
When it’s cold outside, you depend on your furnace to heat your home. But what if it starts up and quickly shuts off again? Let’s investigate.
What are furnace burners?
First, a little about furnace burners and what they do. Furnace burners work much like the burners on a gas stove. Once the gas is ignited, the burners heat one or more heat exchangers, which then heat the air. The blower fan then pushes the warm air into the ductwork and throughout your home.
Trane energy-efficient furnaces have multi-port in-shot burners to perfectly shape the flame cone for the maximum heat possible while using less fuel. They’re enclosed in a sealed combustion chamber that receives air vented in from the outside. Older furnaces use an upshot burner with natural draft venting.
Once the set temperature is reached, the thermostat signals a single or two-stage furnace to shut off. A high-efficiency furnace, or condensing furnace with a modulating gas valve, may run longer at a lower capacity to provide greater comfort and fuel efficiency.
What causes the furnace main burner to shut off?
A lot of things can cause this problem. Most issues will require the help of an HVAC professional.
Issue #1: Dirty or clogged filter
As simple as it seems, a dirty furnace filter can cause the burner to shut off. This is because your furnace needs good airflow to function properly. Restricted airflow can cause the heat exchanger to overheat, triggering the furnace limit switch to shut down the furnace. If your furnace is not blowing hot air, check the filter first.
Issue #2: Problems with the furnace burners
There may be a problem with the furnace burners. An older furnace may suffer from a cracked burner. It may also have rust or other deterioration. A newer furnace might have clogged furnace burners. Too much dirt and grime on the burner can cause it to shut off. Cleaning or replacing the burners may fix the problem.
Issue #3: Problems with the flame sensors
The flame sensor in your furnace is designed to ensure that the gas valve only opens while flames are burning. This prevents gas from building up when there are no flames to burn the fuel. A faulty or dirty flame sensor can malfunction and turn off the furnace prematurely. Furnace flame sensor cleaning or replacing the flame sensor may fix the problem.
Issue #4: Furnace control board problems
Even older standing pilot light furnaces have a control board, although it might not be as sophisticated as the control boards in newer, high-efficiency gas furnaces. The control board is the brain of the furnace and manages the gas valve, ignitor, flame sensor, and even blower motor control (on newer furnaces).
Help prevent problems with furnace maintenance
Be sure to change the furnace filter every 1-3 months year-round. Even in the summer when you’re cooling your home, the furnace works as a blower to circulate cooled air. In addition, schedule a yearly furnace tune-up.
During a furnace maintenance visit, the HVAC technician will examine and clean furnace parts and test the system. If they detect smaller issues, they may make furnace repairs at the same visit. For larger issues, they will schedule a repair visit.
Consider an HVAC maintenance plan for ease of scheduling, priority service, and possibly a discount on parts.
Consider the advantages of Trane Diagnostics
Opt into Trane Diagnostics via the Trane Home App for peace of mind and next-level service. By opting in, you give your dealer remote monitoring capabilities. Your Trane smart thermostat sends real-time data to your dealer, notifying them of problems with your system or when it’s time for HVAC maintenance.
They can run furnace troubleshooting tests to pinpoint a problem. Sometimes, they can solve the problem remotely. In this situation, you would grant them one-time dealer remote access (DRA).
If the issue requires an on-site service call, the HVAC technician will arrive with the knowledge collected during remote access. This enables shorter service calls and ensures the technician has the right replacement parts. This can save both you and the HVAC company time and money.
By Anne Fonda
A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.
She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.
Expert review by Kimberly Sexton, Senior Systems Engineer