Furnace Not Igniting? Common Causes and Solutions
24/7 Emergency Furnace Repair Available
When your furnace fails to ignite on a cold winter day in London Ontario, it's more than an inconvenience—it's an emergency. A furnace that won't start can leave your family shivering and potentially cause frozen pipes. Understanding the common reasons why furnaces fail to ignite can help you troubleshoot simple issues and know when to call for professional help.
In this comprehensive guide, we'll explore the most common causes of furnace ignition problems and their solutions. Remember, while some issues are simple to fix, working with gas appliances can be dangerous. When in doubt, always contact a professional furnace repair service.
Common Reasons Your Furnace Won't Ignite
🔥 Faulty Ignitor
Modern furnaces use hot surface ignitors instead of pilot lights. These can crack or wear out over time, preventing ignition.
🌡️ Thermocouple Issues
The thermocouple is a safety device that detects whether the pilot light is lit. If it's faulty, it won't allow gas to flow.
⛽ Gas Supply Problems
If gas isn't reaching your furnace, it can't ignite. This could be due to a closed gas valve, empty propane tank, or issues with the gas line.
🧼 Dirty Flame Sensor
The flame sensor detects whether burners have ignited. If it's dirty, it may shut down the furnace as a safety precaution.
⚡ Electrical Issues
Problems with your home's electrical system, such as tripped breakers or blown fuses, can prevent furnace operation.
📟 Faulty Control Board
The control board is the furnace's brain. If it malfunctions, it won't send the proper signals for ignition.
Basic Troubleshooting Steps
Before calling for professional help, you can safely check these common issues:
Check Your Thermostat
Ensure thermostat is set to "Heat" and temperature is set higher than current room temperature. Replace batteries if needed.
Inspect Your Circuit Breaker
Check your electrical panel for tripped breakers or blown fuses. Reset any tripped breakers and replace blown fuses.
Verify Gas Supply
Make sure your gas valve is in the "On" position. If you have a propane furnace, check that your tank isn't empty.
Check Air Filters
A severely clogged air filter can restrict airflow and cause your furnace to shut down. Replace dirty filters.
Look for Error Codes
Many modern furnaces have diagnostic lights that flash error codes. Consult your owner's manual to interpret these codes.
If you smell gas at any point, leave your home immediately and call your gas company from a safe location. Do not attempt to troubleshoot gas-related issues yourself.
What Ontario Homeowners Say About Ignition Repair
"Our furnace wouldn't ignite on the coldest night of the year. Called Hawana and Abdullah arrived within 90 minutes. He diagnosed a cracked ignitor, had a replacement on his truck, and had heat back on within 2 hours. Zero after-hours surcharge. Great service and fair pricing. Saved us from frozen pipes."
— Holm B. London ON · December 2025
"Our furnace kept starting then shutting off after 5 seconds. This guide pointed to the flame sensor. Abdullah came out, cleaned the flame sensor, and the furnace works perfectly. He explained that annual maintenance prevents this. Signed up for their maintenance plan. Great service and honest advice."
— Clove T. London ON · January 2025
"Our old furnace with a pilot light wouldn't stay lit. Abdullah diagnosed a bad thermocouple. He replaced it and the furnace works great. Also pointed out that our furnace was 22 years old and recommended planning for replacement. Honest advice, not pushing an unnecessary sale. Highly recommend Hawana for furnace ignition issues."
— Gorse K. London ON · February 2025
Abdullah Ghzail – Owner & Lead TSSA-Certified HVAC Specialist
"After thousands of furnace service calls, the most common ignition problem I see is a cracked ignitor in modern furnaces. These components wear out over time and are a simple fix when caught early. The second most common is a dirty flame sensor—a 5-minute cleaning during annual maintenance prevents this. Don't wait for a no-heat emergency. Schedule annual maintenance and catch these issues before winter. If your furnace won't ignite, call us immediately. We'll diagnose the problem and restore heat quickly."
Furnace Ignition FAQ – 2025
Common reasons include a faulty ignitor (most common in modern furnaces), thermocouple issues (older furnaces with pilot lights), gas supply problems (closed valve or empty propane tank), dirty flame sensor, electrical issues (tripped breaker), or a faulty control board. Our TSSA-certified technicians can diagnose and fix these problems quickly, usually within 1-2 hours of arrival. Call us for immediate assistance.
First, check your thermostat settings (ensure it's set to 'Heat' and temperature is above room temperature) and circuit breaker. Replace batteries if needed. If these are fine, it's best to call a professional. Attempting DIY repairs on gas appliances can be dangerous. Our emergency furnace repair team can diagnose and fix the issue safely, usually within 2-4 hours of your call. We provide upfront pricing before any work begins.
A pilot light that won't stay lit often indicates a faulty thermocouple, which is a safety device that shuts off gas if it doesn't detect a flame. Other causes include draft issues, low gas pressure, or a dirty pilot orifice. This requires professional diagnosis and replacement for safety. If you have an older furnace with a pilot light, consider upgrading to a modern electronic ignition furnace for better reliability and efficiency.
We offer 24/7 emergency furnace repair with most calls responded to within 2-4 hours. For no-heat emergencies in winter, we prioritize these calls and can often arrive within 1-2 hours. We charge zero after-hours surcharge—same price day or night. Our technicians carry common ignitor and flame sensor models for quick repairs. Call our emergency line at (647) 550-4220 for immediate assistance.
A hot surface ignitor is a silicon carbide or silicon nitride component that glows red hot to ignite gas in modern furnaces. They typically last 5-10 years depending on usage and environmental factors. Signs of failure include visible cracks, white spots, or the furnace clicking but not igniting. Replacement cost is typically $150-$350 including labor. We carry common ignitor models on our trucks for same-day replacement. Annual maintenance includes ignitor inspection.
The flame sensor detects whether burners have ignited. If it's dirty or coated with carbon, it may shut down the furnace as a safety precaution, causing short cycling or complete failure to ignite. Cleaning the flame sensor (annual maintenance task) resolves this issue. Signs include the furnace starting then shutting off after 3-5 seconds. Professional cleaning costs $100-$200 and is included in our maintenance plans. Regular cleaning prevents ignition problems.
Yes. A tripped circuit breaker or blown fuse will prevent your furnace from receiving power, causing it not to ignite. Check your electrical panel for a tripped breaker labeled 'furnace' or 'HVAC'. Reset it by flipping fully off then on. If it trips again immediately, call a professional—this indicates an electrical issue that needs diagnosis. Don't repeatedly reset a tripping breaker. Electrical problems can be caused by failing components.
If you smell gas at any point, leave your home immediately. Do not operate light switches, electrical devices, or phones inside the house. Call your gas company's emergency line or 911 from a safe location outside. Do not re-enter until emergency services declare it safe. A gas smell indicates a potential gas leak, which is a serious safety hazard. Never attempt to troubleshoot gas-related issues yourself. Gas leaks can cause explosions and carbon monoxide poisoning.
Furnace ignition repair costs vary: ignitor replacement $150-$350, flame sensor cleaning $100-$200, thermocouple replacement $150-$300, control board replacement $350-$750, gas valve repair $200-$500. Diagnostic fee typically $89-$149 (often waived if repair proceeds). Most ignition repairs are completed within 1-2 hours. We provide upfront pricing before starting any work. Regular maintenance plans include diagnostic coverage and discounts on repairs.
Prevent furnace ignition problems with annual professional maintenance ($149-$249/year) that includes cleaning flame sensors, inspecting ignitors, checking gas pressure, testing safety controls, and cleaning burners. Regular filter changes (every 1-3 months) also help prevent airflow issues that can affect ignition. Our maintenance plans include comprehensive ignition system checks and priority emergency service. Most ignition problems are preventable with regular maintenance.
Need Emergency Furnace Repair in London Ontario?
Don't risk your family's comfort or safety with a malfunctioning furnace. Our TSSA-certified technicians provide 24/7 emergency service across London and Southwestern Ontario.
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