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Furnace Burners Not Igniting: Causes and Fixes

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A properly functioning furnace is necessary to keep your home warm and comfortable. When your gas furnace won’t ignite, it can leave you scrambling for a solution. Continue reading to discover common causes of ignition failure and explore solutions for ignition challenges.

Furnace Burner Basics

A furnace burner is the heart of your heating system, responsible for creating the heat that warms your home. By familiarizing yourself with the key components of your heating system, you will be better equipped to identify and address why your furnace burner won’t stay lit.

Components of a Furnace Burner

Most modern furnaces consist of the following basic parts:

  • Gas orifice: Controls the flow of gas into the burner.
  • Venturi tube: Mixes gas with air to create a combustible mixture. 
  • Igniter: Provides the spark or heat to light the gas.
  • Flame sensor: Detects the presence of a flame and signals the gas line to remain open.

Apart from these, older furnaces may have a pilot light, a small, continuously burning flame that ignites the main burner when the furnace is ignited to operate. Modern furnaces often use electronic ignition systems, such as intermittent pilot light ignition or hot surface ignition, instead of a standing pilot light.

Types of Furnace Burners

Modern furnaces are designed to operate using different fuel sources, each with its own advantages and considerations. The two most common types of furnace burners are natural gas burners and alternative fuel burners.

Natural gas is the most widely used fuel source for residential and commercial furnaces due to its cost-effectiveness and relatively clean burning properties. Alternative fuel sources for furnaces include propane, oil furnaces, and electricity, which may be preferred in areas where natural gas is not readily available. When choosing a furnace burner type, consider factors such as local fuel availability, installation and maintenance costs, ratings, and environmental impact.

How Burners Work

When your thermostat signals a need for heat, the gas line opens, allowing gas to flow into the burner. Simultaneously, the igniter generates a spark or heats up to ignite the gas. Once the flame sensor detects a stable pilot flame, the burner continues to operate until the desired temperature is reached.

Most Likely Reasons Furnace Burners Won’t Light

Understanding the potential causes behind a dysfunctional furnace is the first step in resolving the issue and restoring heat to your home. Several factors can contribute to furnace burners failing to ignite. Here are some of the most common culprits:

  • Thermostat Issues: If your thermostat is not functioning correctly or is set improperly, it may not signal your furnace to ignite. Check that your thermostat is set to “heat” mode and the desired temperature is higher than the current room temperature.
  • Blocked or Dirty Burner: Over time, burners can accumulate dirt, debris, or even rust, obstructing the flow of gas and preventing ignition. Regularly inspecting and cleaning your burners is crucial for optimal performance.
  • Ignition System Malfunctions: Faulty igniters or worn-out ignition components can hinder the burner from lighting. This may involve a malfunctioning hot surface igniter, a cracked ignition electrode, or a faulty ignition control module.
  • Gas Supply Problems: If your furnace isn’t receiving a steady gas supply, the burners won’t ignite. This could be due to a closed gas valve, a leak in the gas line, or insufficient gas pressure from your utility provider.
  • Compromised Circuit Board: The circuit board controls the furnace’s electronic components. If it becomes damaged or experiences a short circuit, it may fail to send the necessary signals to ignite the burners.
  • Damaged Sensor: A dirty or malfunctioning pilot flame sensor can incorrectly detect the absence of a pilot flame, causing the valve to close prematurely and preventing consistent burner operation.
  • Airflow Restrictions: Proper airflow is essential for burner combustion. Clogged air filters, blocked vents, or a malfunctioning blower motor can restrict airflow and hinder ignition.
  • Malfunctioning Limit Switch: The limit switch is a safety device that shuts off the burners if the furnace overheats. If this switch malfunctions, it may prevent the burners from igniting even when there is no overheating risk.

Troubleshooting Your Furnace Burner

Once you determine the cause of your heating system’s problem, take action to resolve the issue. Some issues may require professional assistance, but other common problems can be diagnosed and fixed by homeowners.

  • Addressing Thermostat Issues: Double-check your thermostat settings and batteries. If the problem persists, consult your thermostat manual or contact a professional HVAC technician for assistance.
  • Cleaning or Replacing the Burner: Turn off the gas and power to your furnace before attempting any cleaning or repairs. Use a soft brush or compressed air to remove dirt and debris from the burner. If the burner is damaged or corroded, replacement may be necessary. For a more detailed description, follow our step-by-step guide to clean your furnace.
  • Resolving Ignition Malfunctions: Inspect the igniter and ignition components for cracks, damage, or excessive wear. Replace any faulty parts and confirm proper connections.
  • Continuous Gas Supply: Verify that your gas valve is fully open and there are no leaks in the gas line. Contact your gas utility company if you suspect low gas pressure or supply issues.
  • Dealing with a Compromised Circuit Board: If you suspect a damaged circuit board, it’s best to call a professional HVAC technician for an accurate diagnosis and repair.
  • Repairing the Pilot Flame Sensor: Carefully remove the pilot flame sensor and clean it with fine-grit sandpaper or steel wool. If the sensor is damaged, replace it with a new one.
  • Improving Air Flow: Replace clogged air filters, clear any blocked vents, and check your blower motor functions properly to maintain adequate airflow.
  • Checking and Replacing the Limit Switch: Test the limit switch for continuity using a multimeter. If it’s faulty, replace it with an identical switch designed for your furnace model.

A furnace burner that won’t ignite can be a frustrating and chilly experience. By understanding the common causes and following the troubleshooting steps described above, you can often resolve the issue yourself.

Contact a qualified HVAC technician to assist you in furnace maintenance. With prompt attention to malfunctions, you can keep your furnace burners igniting reliably and maintain comfortable indoor temperatures.

The Logan Difference

At Logan A/C & Heat, we are more than just your average HVAC company. As a family-owned and operated business, we treat our customers like family. That’s why we go above and beyond to guarantee that every installation is done right, with the utmost care and attention to detail.

Our installers undergo a rigorous training program to verify they have the skills and knowledge necessary to provide valuable service. We believe in the power of communication, which is why our installers follow a comprehensive checklist that is signed off on by our experienced install managers. Every installation is completed to our high standards, and no detail is overlooked.

At Logan A/C & Heat, we believe that our job isn’t finished until you are completely satisfied. That’s why we conduct a thorough walkthrough with you after every installation. Our installers will show you how to set up and troubleshoot your new system and answer any questions you may have.

When you choose Logan A/C & Heat, you’re not just choosing an HVAC company. You’re choosing a partner who will be there for you every step of the way. That’s the Logan Difference. Contact us today for all your furnace and HVAC needs.

Frequently Asked Questions

How often should I clean my furnace burners?

Experts recommend cleaning your furnace burners at least once a year, preferably before the heating season begins. Regular maintenance ensures efficient operation and prolongs the life of your furnace. If you notice signs of decreased performance, such as inconsistent heating or unusual sounds, it may be necessary to clean the burners more frequently or consult with a professional HVAC technician.

Why does my furnace keep shutting off shortly after igniting?

If your furnace shuts off shortly after igniting, it may be due to a malfunctioning flame sensor. The sensor may be dirty or damaged, preventing it from detecting the flame and causing the valve to close prematurely. This issue, known as short cycling, might also be caused by other factors such as overheating, improper thermostat settings, or a clogged air filter restricting airflow. Troubleshoot early shutdown with these tips.

How do I know if my furnace’s ignition system is faulty?

Signs of a faulty system include clicking sounds without ignition, intermittent pilot igniters, or the burner failing to light at all. You may additionally notice your furnace’s blower running without heat production.

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