A delayed or failed furnace ignition can leave you shivering on cold winter nights. Understanding common furnace ignition issues can help you identify and resolve problems before they become dangerous or costly. This guide covers the causes, risks, and repair options for ignition failure in natural gas and oil furnaces.
What Causes Furnace Ignition Failure?
Normal furnace operation requires a spark from the ignition system to light the gas or oil burner. Anything that interferes with the ignition spark or fuel supply can prevent successful ignition. Common culprits include:
- Faulty Igniter or Flame Sensor – These electronic components create the spark for ignition. If they malfunction, no spark occurs to light the burner. Cracked igniter insulation or a dirty flame sensor could be the issue.
- Clogged Burners or Heat Exchanger – Buildup of lint, soot, and debris can block the burners or heat exchanger passages. This prevents proper ignition and combustion.
- Gas Valve Defect – Defective gas valves fail to release the right amount of fuel for proper ignition. This includes gas valves that leak continuously or fail to open.
- Improper Gas Flow – Restricted gas lines caused by moisture, corrosion, kinks, or leaks reduce fuel flow. Without enough gas flow, ignition will fail or be delayed until adequate gas builds up.
- Improper Gas Pressure – Gas pressure that is too high or low will affect the air-fuel mix required for ignition. Gas pressure must be within specifications.
- Pilot Light Issue – A clogged or blown pilot light assembly will fail to ignite the burner. Common with older furnaces, especially those using standing pilots.
- Ignition Control Failure – The ignition control board can malfunction and fail to send voltage to the igniter or gas valve as needed for ignition.
- Blown Fuse – Power surge or electrical issue can blow a furnace fuse and disable ignition components.
- Improper Venting – Inadequate combustion air supply or vent blockage affects ignition. Proper venting and air intake are essential.
- Damaged Combustion Chamber – Cracks in the combustion chamber or heat exchanger allow air leaks that disrupt ignition.
- Poor Maintenance – Lack of annual furnace inspection and cleaning increases ignition failure risk. Keep your HVAC system maintained.
Dangers of Ignition Failure
Delayed or failed ignition creates several risks including:
- Gas Buildup and Explosion – Unignited gas can build up in the combustion chamber and explode when ignition eventually occurs. Repeated small explosions strain the furnace.
- Carbon Monoxide Leak – Gas leaks or improper combustion releases deadly carbon monoxide into living spaces.
- Fire Hazard – Gas leaks, auto ignition of built up gas, or unburned fuel increase fire risk. Failed ignition also requires manually lighting the furnace, which is extremely dangerous.
- Heating Failure – Ignition issues lead to lost heat, frozen pipes, and uncomfortable indoor temperatures. Elderly, infants, and pets are especially vulnerable.
- Furnace Damage – Repeated forced ignition attempts when older furnaces fail to light stresses components. Explosions from delayed ignition also damage the heat exchanger, burners, and other parts over time.
Repairing Ignition Problems
Only qualified HVAC technicians should diagnose and repair ignition issues. They can perform in-depth troubleshooting and repairs such as: - Replacing faulty igniters, flame sensors, pilot assemblies and other ignition components
- Cleaning burners and the heat exchanger if blocked
- Adjusting gas pressure and testing for leaks
- Fixing electrical issues like blown fuses or defective control boards
- Correcting venting or combustion air supply problems
- Repairing or replacing damaged gas valves or piping
- Updating old standing pilot furnaces to electronic ignition models
Prevention is ideal. Follow your manufacturer’s maintenance schedule and have your furnace inspected annually before winter. Replace old standing pilot furnaces with safer electronic ignition models. Install carbon monoxide detectors for early warning of improper combustion.
Rely on a Reputable HVAC Company for Furnace Repairs
Ignoring ignition failure leads to danger, discomfort and damage. For professional diagnosis and repair of any furnace ignition problems, contact Mauzy Heating, Air & Solar. Our NATE-certified technicians have the training, experience and digital tools to accurately troubleshoot your system. We serve San Diego County with honest, transparent and cost-effective HVAC repair solutions. Protect your home and family this winter with proper furnace maintenance and ignition system repairs from the experts at Mauzy.