7 Possible Reasons Your Gas Furnace’s Pilot Light Won’t Stay Lit
Does your furnace’s pilot light keep going out? Have you woken up at night or returned from work, only to find that your home is nearly as cold as it is outside? The reason may be that the pilot light in your heater won’t stay on.
Addressing this issue is a common gas furnace repair. Your furnace can’t produce heat if the flame doesn’t stay lit, because it won’t be able to initiate combustion. Relighting the flame can quickly resolve the matter. If the pilot light keeps going out, the furnace should be repaired by an HVAC professional.
Pilot light problems are most common in older gas furnaces. Their causes include faulty components, dirt, or a draft. A faulty pilot light can waste fuel and energy. It’s also a safety concern, as a combustion issue can result in a carbon monoxide leak.
Here are some common reasons your furnace pilot light won’t stay lit:
1. Faulty Thermocouple Preventing Flame Detection
Often called the flame sensor, the thermocouple is a copper tube positioned in the path of the pilot flame. It keeps the gas valve open when it senses high temperatures. If it detects no heat, it triggers the valve to close. Therefore, the thermocouple is a safety feature that prevents gas from flowing into your home or a furnace that’s not working properly.
The thermocouple can malfunction for a few reasons. It may be unable to detect the flame due to:
- Damage: The component can break or burn out, preventing it from detecting the flame. It must then be replaced.
- Dirt: Soot and residue can accumulate from prolonged exposure to the flame. The thermocouple can be cleaned with a wire brush or coarse material.
- Misalignment: The flame should cover the top of the thermocouple. If not, the device won’t sense the flame and will turn off the gas.
Fortunately, thermocouple replacement or cleaning is a fast and simple furnace repair for a trained professional.
2. Clogged Pilot Orifice Restricting Gas Flow
Natural gas reaches the pilot light via an orifice. If this opening becomes dirty, the flow of gas can be disrupted, weakening the pilot flame. It should always be a strong blue color. However, if the flame looks weak or yellow, the issue must be addressed promptly, as a carbon monoxide leak can occur.
A dirty pilot orifice is a common reason for a weak flame. Clearing out the debris can resolve the problem, but it requires disassembling the pilot mechanism. Professional skills are needed to do this safely and successfully. A furnace technician can clean out the orifice during routine maintenance.
3. Gas Valve Issues Disrupting Fuel Delivery
Since the gas valve is what delivers gas to the pilot light, the flame won’t stay lit if it malfunctions. Replacing the valve is usually the only option. This restores the flow of natural gas so the pilot system and your furnace can work properly. Repairs also eliminate a potential gas leak that can be harmful if inhaled or cause a fire; they can address electrical issues (with a valve coil or wire) that are hazardous as well.
4. Blocked or Damaged Pipe Affecting Gas Flow
The gas pipe connected to your furnace can get clogged over time. Debris, rust, and other materials can contaminate the line and restrict gas flow. Signs of a clogged gas inlet pipe include:
- The furnace doesn’t turn on
- The system won’t shut off
- Reduced heating performance
- Uneven heating in your home
- Foul odors from your furnace
Contact a gas furnace repair professional if you suspect the gas line is blocked. Only a licensed contractor with experience fixing gas lines should attempt to repair this problem.
5. Drafts or Airflow Disrupting Pilot Flame
A draft affecting the pilot light is another reason it can go out, especially if it relights easily. The issue is often easily fixable. But it can range from strong airflow in the area around your furnace to a heating or ventilation problem. Common causes of air extinguishing a pilot flame include:
- Drafts from strong winds enter gaps in exterior walls.
- Closed intake air registers create a vacuum effect.
- Poor insulation around windows and doors.
- Restricted airflow from dirt or soot.
- A leak from the furnace’s output duct.
If the pilot light goes out frequently, the outlet duct may be leaking. This duct exhausts
hot air from the furnace; a leak can force air towards the pilot. A professional can seal
the duct to fix the problem. However, a more serious problem is a leak involving the
exhaust pipe or flue, which can cause gas to build up in your home. Turn off your
furnace and call an HVAC professional if there’s a draft near the exhaust vent.
6. Malfunctioning Gas Regulator Affecting Pressure
The gas pressure regulator is a crucial component of your heating system. It reduces the pressure of incoming gas to a lower and more consistent level. Therefore, your furnace can operate more safely with a minimal risk of a leak or explosion.
A pressure regulator may be built into the furnace, installed at the gas meter, or located somewhere along the gas line. If it malfunctions, the flow of gas to the furnace may be blocked. Or, it can rupture, causing a gas leak. Call your local utility company if your furnace isn’t working properly or if multiple household appliances are affected.
Other signs of an issue include:
- Gas odors near the regulator
- Inconsistent gas pressure
- Hissing sounds at the gas meter
7. A Utility Disruption Reducing Gas Availability
If the pilot light keeps going out, the underlying issue may not be with your furnace. A problem with your local gas supply can reduce the amount of fuel available to your appliances. Due to high demand or limited availability, gas may flow at reduced pressure. If this is the case, gas fixtures and appliances throughout your home will be affected, and your neighbors will experience the same problem. You should call a professional or your local utility just to be sure. Unfortunately, the issue can’t be resolved until the utility company fixes it.
Frequently Asked Questions
Where Is the Pilot Light on My Furnace?
If you have an older gas furnace, its pilot light is usually at the bottom. You can find it behind a small front access panel or see it through a small window. If you can’t find the pilot light, check the appliance’s owner’s manual.
How Do I Restart a Furnace Pilot Light?
If you feel comfortable doing so, here’s how to relight the pilot:
- Turn the gas valve to the “Off” position.
- Wait 3 minutes, and then turn the valve to “Pilot”.
- Hold a lit match near the pilot opening (about 1-3 inches away from it), and push the “Reset” button on the pilot control panel.
- Press the button down until the flame lights up.
- Move the knob to the “On” position.
How Do I Turn Off the Pilot Light on a Furnace?
You don’t need to access the pilot light itself. Instead, locate the gas valve and move it to the “Off” position. It usually has a label. If there isn’t a dial, make sure the valve is perpendicular to the gas pipe to ensure it’s turned off.
When to Contact a Professional HVAC Technician
Call a professional when the furnace pilot light won’t stay lit or if it repeatedly goes out. These are signs of an internal problem with the appliance. Also, call for help in the following situations:
- The pilot flame won’t light.
- You hear hissing or other unusual sounds.
- There are unusual odors from the furnace/gas line.
- Gas pressure is fluctuating.
- Adjusting the gas valve is difficult.
- The pilot light is flickering or yellow.
Call C & C Heating & Air Conditioning
If your gas furnace pilot light won’t stay lit, it’s essential to address the issue promptly to ensure your comfort and safety. The certified technicians at C & C Heating & Air Conditioning are experienced at diagnosing and fixing a wide range of problems with Lennox, Carrier, Trane, and other leading-brand heating systems. Our team is available 24/7 for emergency service.
Contact us for gas furnace repair, or, if heater replacement is required, to learn about your options, HVAC maintenance packages, and rebates or tax credits.
