The pilot light on a gas furnace is a small flame that ignites the burners. When the pilot is out on a furnace, the system will not produce heat and may present safety concerns. This article explains common causes, safe relighting procedures, troubleshooting steps, and when to call a professional to restore safe operation.
| Issue | Quick Action | When To Call A Pro |
|---|---|---|
| Pilot Light Out | Relight per manufacturer instructions; check gas valve and wiring | If it won’t stay lit or smells like gas |
| Gas Odor | Evacuate and call gas company immediately | Always |
| Thermocouple Fault | Inspect and replace if faulty | If relighting fails repeatedly |
| Clogged Pilot Orifice | Clean or have cleaned | If cleaning doesn’t help |
How A Furnace Pilot Light Works
The pilot light provides a continuous flame that ignites the furnace burner when the thermostat calls for heat. Modern furnaces may use an electronic ignition instead of a standing pilot. The pilot assembly includes the pilot orifice, thermocouple (or thermopile), pilot tube, and gas valve. Proper operation of these components is essential for safe ignition.
Common Reasons The Pilot Is Out On A Furnace
Several factors can cause the pilot out on a furnace. Identifying the cause guides the correct remedy.
- Drafts Or Airflow: Strong drafts or improper venting can blow out a standing pilot.
- Dirty Pilot Orifice: Dirt or debris can restrict gas flow and weaken the flame.
- Faulty Thermocouple: A failing thermocouple will not sense the flame and will shut off gas to the pilot.
- Gas Supply Issues: Closed valves, low pressure, or supply interruptions will extinguish the pilot.
- Wear And Age: Components degrade over time and fail to keep the pilot lit.
Safety First: What To Do If There Is A Gas Smell
If a gas odor is present, immediate safety actions take priority. Do not attempt to relight the pilot.
- Evacuate the building immediately and avoid using electrical switches or open flames.
- From a safe distance, call the gas company emergency number or 911.
- Do not re-enter until a qualified technician or the gas utility confirms it is safe.
How To Relight A Pilot On A Furnace Safely
Before relighting, read the furnace’s manufacturer instructions posted on the unit or in the manual. The following are general steps that apply to many standing-pilot systems.
- Turn off the thermostat and set the furnace switch to OFF.
- Shut off the gas supply by turning the furnace gas valve to the OFF position.
- Wait five minutes to allow any residual gas to clear.
- Locate the pilot assembly and set the gas valve to PILOT.
- Press and hold the pilot button or knob while using the built-in igniter or a long match/utility lighter to ignite the pilot.
- Keep the pilot depressed for 30–60 seconds after ignition to allow the thermocouple to warm and signal the gas valve to stay open.
- Release the knob slowly; if the pilot stays lit, switch the valve to ON and restore power to the furnace.
If the pilot does not stay lit after several attempts, stop and proceed to troubleshooting or call a professional.
Troubleshooting When The Pilot Won’t Stay Lit
When the pilot is out on a furnace and will not remain lit, targeted diagnostics help identify the faulty component.
Check The Thermocouple
The thermocouple senses the pilot flame and keeps the gas valve open. A weak or broken thermocouple often causes the pilot to go out.
- Inspect for corrosion, soot, or misalignment from the flame.
- Ensure the pilot flame touches the thermocouple tip; the flame should be steady and blue.
- Replacement is a common fix and is often inexpensive and straightforward for a qualified person.
Inspect The Pilot Orifice
A clogged pilot orifice reduces gas flow and produces a small, weak flame that may not heat the thermocouple.
- Turn off gas and power before attempting any cleaning.
- Use compressed air or a fine wire to clear debris carefully; avoid enlarging the orifice.
- If uncomfortable cleaning, schedule a service call to avoid damage.
Verify Gas Supply And Valves
Confirm the household gas supply is on and other gas appliances are working. Inspect the furnace gas shutoff valve for correct position. If multiple gas appliances are not functioning, contact the gas utility.
Check For Drafts And Venting Problems
Pilot lights can be extinguished by drafts or improper venting. Verify vents and flues are clear of obstructions and that external wind is not blowing directly into the vent termination.
When To Call A Professional
Some situations require a licensed HVAC technician or gas utility representative.
- Persistent Pilot Failure: If the pilot will not stay lit after cleaning and thermocouple replacement.
- Gas Odor Or Leak Suspicion: Evacuate and call the gas company or emergency services.
- Complex Issues: Problems with the gas valve, control module, or flue require professional diagnosis.
- Older Furnaces: If the furnace is old or unsafe, a technician can advise on repair versus replacement.
Costs And Parts To Expect
Repair costs vary based on the issue and region. Typical items and price ranges provide context.
| Item | Typical Cost Range |
|---|---|
| Thermocouple Replacement | $50–$150 Parts And Labor |
| Pilot Orifice Cleaning | $75–$150 Service Call |
| Gas Valve Replacement | $200–$600+ |
| Service Call Diagnostic Fee | $75–$150 |
Costs vary widely. Obtain multiple quotes for major repairs and confirm technician licensing and insurance.
Preventive Maintenance To Avoid Pilot Out Issues
Regular maintenance reduces the chance the pilot is out on a furnace and extends equipment life.
- Schedule annual professional furnace service before heating season.
- Replace air filters monthly during heavy use to maintain airflow and reduce dust near the pilot assembly.
- Keep the area around the furnace clean and free of drafts or strong air currents.
- Have the pilot assembly and orifice inspected and cleaned periodically.
- Test carbon monoxide detectors and ensure proper venting to prevent dangerous conditions.
Electronic Ignition Alternatives
Many modern furnaces use electronic ignition systems such as hot-surface igniters or intermittent pilots. These systems eliminate a standing pilot, improving efficiency and reducing the specific pilot-out problem.
- Electronic ignitions are more energy-efficient and often more reliable.
- Failures in these systems show different symptoms, such as repeated ignition attempts or error codes on the furnace control board.
- Upgrading to electronic ignition can be cost-effective over time through energy savings and fewer service calls.
Frequently Asked Questions
Is It Safe To Relight A Pilot On A Furnace?
Relighting a pilot per the manufacturer’s instructions is safe if there is no gas smell and the user follows precautions. If a gas odor is detected or the user is unsure, contact the gas utility or a professional.
Why Does The Pilot Keep Going Out After Being Relit?
Repeated outages often indicate a thermocouple problem, dirty pilot orifice, gas supply issues, or drafts. Professional diagnosis is recommended if basic cleaning and alignment do not resolve the issue.
Can A Homeowner Replace A Thermocouple?
Many homeowners with basic mechanical skills can replace a thermocouple after shutting off gas and power. However, due to the safety implications, hiring a licensed HVAC technician is often recommended for proper installation and testing.
Additional Resources And Codes
Local building codes and gas utility rules govern furnace safety and repairs. Refer to the furnace manufacturer manual and local utility guidelines for specific instructions.
For persistent issues or any suspected gas leak, contact the gas company and a licensed HVAC professional. Prioritizing safety and following proper procedures keeps occupants and property protected.