A gas furnace pilot light going out can leave a home chilly and raise safety concerns. Understanding why the pilot light goes out and how to safely relight it helps maintain comfort and safety. This guide covers common causes, essential safety steps, relighting procedures for standing-pilot furnaces, and when to call a professional. It also offers practical tips to prevent future outages and keep a furnace operating efficiently.
What Causes A Gas Furnace Pilot Light To Go Out
A pilot light that won’t stay lit is usually caused by one or more mechanical or gas-supply issues. Drafts near the furnace, improper venting, or backdrafts can blow out a flame. A dirty or misaligned thermocouple or pilot orifice can also intermittently extinguish the flame. In some cases, low or unstable gas pressure from the supply line or malfunctioning gas valve prevents reliable ignition. Aging components, including the pilot assembly and regulator, may degrade and fail to sustain a flame over time.
- Drafts or backdrafts from poor venting or nearby openings
- Dirty, corroded, or misaligned thermocouple or pilot orifice
- Gas pressure issues or a faulty gas valve
- Low gas supply or shutoff valves partially closed
- Aging furnace components or improper installation
- Obstructions around the pilot assembly or vents
Safety Considerations When a Pilot Light Goes Out
Safety is the top priority when a pilot light goes out. A failed flame may indicate a gas leak risk, or a malfunctioning appliance that could produce carbon monoxide. If a strong gas odor is detected or there is any suspicion of a leak, evacuate the area and call emergency services or the gas supplier from a safe location. Do not operate electrical switches or create sparks near the furnace. Ensure the space is well-ventilated and verify that carbon monoxide detectors are functioning. Only attempt relighting after confirming there is no gas odor and the area is safe.
- Do not light switches, electrical devices, or sources of flame in the area
- Ventilate the space if a mild odor is present; leave if the odor intensifies
- Check for a working carbon monoxide detector near the furnace and in the home
- If you smell gas, leave immediately and contact the gas company or emergency services
- Only attempt relighting if there is no gas odor and you know the area is safe
How To Relight A Gas Furnace Pilot Light
Relighting procedures differ between furnaces with a standing pilot and those with electronic ignition. The following steps assume a standing-pilot furnace. If your unit uses electronic ignition, use the manufacturer’s instructions or contact a professional.
- Turn the thermostat to OFF and locate the furnace access panel.
- Open the panel and locate the gas control knob. Turn it to OFF and wait 5 minutes to clear any accumulated gas.
- Move the knob to PILOT mode.
- Press and hold the reset/ignite button (or a designated spark button) while using a long lighter to ignite the pilot flame at the burner.
- Keep holding the knob in the PILOT position for 30–60 seconds after the flame appears to ensure the thermocouple heats and the valve stays open.
- Release the button and slowly turn the control to ON. Close the access panel and restore power to the furnace if needed.
- Set the thermostat to a desired temperature and verify that the furnace starts and the flame remains steady.
Note: If the pilot flame is yellow or flickers, or if the flame dies shortly after relighting, the problem may be a dirty pilot port, a failed thermocouple, or a defective gas valve. In these cases, do not repeatedly relight and contact a professional for diagnosis and repair.
What To Do If The Pilot Keeps Going Out
Frequent relighting usually signals an underlying issue. A misaligned thermocouple, a dirty pilot orifice, or an unstable gas supply are common culprits. Drafts or improper venting can also cause repeated outages. If relighting fails repeatedly, or if the flame is weak, yellow-tipped, or accompanied by unusual noises, stop and call a licensed technician. Regular maintenance can address these problems and prevent future outages, improving reliability and safety.
- Inspect and clean the pilot and thermocouple if accessible, following the manual
- Check for drafts near the furnace and improve enclosure or venting
- Test gas pressure with appropriate equipment or request a service check
- Schedule annual furnace maintenance to catch wear and corrosion early
When To Call A Professional
Some situations require professional intervention. If the pilot light repeatedly goes out after relighting, or if the flame remains weak or unstable, a technician should assess the thermocouple, gas valve, regulator, and ignition system. If there is any suspected gas leak, if the furnace is unusually old, or if carbon monoxide alarms trigger, contact a licensed HVAC technician immediately. Do not attempt complex repairs beyond basic relighting without proper training.
- Pilot refuses to stay lit after relighting attempts
- Weak, flickering, or yellow flame persists
- Repeated gas odors or CO detector activation
- Suspected gas valve or regulator failure
- Older furnaces showing signs of corrosion or wear
Preventive Tips To Avoid Pilot Light Going Out
Preventive maintenance helps minimize incidents of a gas furnace pilot light going out. Regular service by a qualified technician, replacement of aging components, and proper venting reduce risk and improve efficiency. Simple practices like keeping the furnace area clear of clutter, replacing dirty air filters, and ensuring proper gas supply can extend the life of the pilot system. Installing and testing carbon monoxide detectors in key home areas adds an essential safety layer.
- Schedule annual furnace inspection and cleaning
- Replace thermocouples and pilots according to manufacturer recommendations
- Keep intake and exhaust vents free from obstructions
- Check gas lines and shutoff valves for signs of wear or leaks
- Maintain working carbon monoxide detectors on every floor