A pilot light is supposed to be the quiet, steady heartbeat of a gas appliance. So when it keeps going out—again and again—it’s more than annoying. It can mean cold showers, a furnace that won’t kick on, or a stove that suddenly feels unreliable. The good news is that many pilot-light issues come down to a handful of common causes, and you can often narrow them down safely with a little step-by-step troubleshooting.
This guide walks through what a pilot light does, why it fails, and what you can check without taking risks. We’ll also talk about when it’s time to stop tinkering and call a pro—because with gas appliances, “almost fixed” isn’t the same as safe.
What the pilot light actually does (and why it’s easy to underestimate)
On older gas appliances, the pilot light is a small, continuously burning flame. Its job is to ignite the main burner when the appliance calls for heat—like when your water heater needs to warm the tank or your furnace needs to heat the house. If the pilot flame goes out, the appliance can’t light the main burner, and everything shuts down.
Modern appliances often use electronic ignition instead of a standing pilot, but plenty of water heaters, fireplaces, and older furnaces still rely on the classic pilot setup. That means a tiny flame is responsible for a lot of comfort—and a small change in airflow, gas pressure, or a safety sensor can snuff it out.
It’s also worth noting: a pilot that won’t stay lit is sometimes the appliance doing its job. Safety devices are designed to shut off gas flow if they detect a problem. So the “failure” is often a clue that something needs attention.
Before you touch anything: quick safety checks that matter
Trust your nose and your senses
If you smell gas (a sulfur or “rotten egg” odor), don’t try to relight the pilot. Leave the area, avoid flipping switches or using open flames, and follow your local gas utility’s emergency guidance. A pilot light issue is never worth gambling with.
Also pay attention to symptoms like soot around the burner area, headaches or dizziness when the appliance runs, or a “whooshing” sound at ignition. Those can point to combustion or venting issues that need professional diagnosis.
Give the appliance a cool-down window
If the pilot just went out, wait a few minutes before attempting anything. Gas valves and burners can be hot, and some appliances need time to clear any unburned gas from the combustion chamber.
While you wait, open a nearby window for fresh air. Extra ventilation is helpful if you’re going to inspect the area (even if you don’t smell gas).
Know where the shutoff is—just in case
It’s smart to locate the gas shutoff valve to the appliance before you begin. On many water heaters, it’s a valve on the gas line near the unit; on some appliances, there’s also a control knob on the gas valve assembly. If anything feels off, you’ll want to be able to shut things down quickly.
If you’re not sure what you’re looking at, don’t force anything. A quick photo and a call to a professional can prevent accidental damage.
How a pilot light is supposed to stay lit
The thermocouple (or thermopile) is the gatekeeper
In many standing-pilot systems, the pilot flame heats a small metal sensor called a thermocouple (or a thermopile in some designs). When heated, it generates a tiny electrical signal that tells the gas valve, “The flame is present; it’s safe to keep gas flowing.”
If the thermocouple doesn’t get hot enough—or if it’s dirty, damaged, or misaligned—the gas valve closes and the pilot goes out. This is one of the most common reasons a pilot won’t stay lit after you release the control knob.
Stable airflow and clean combustion keep the flame steady
A pilot flame needs a consistent mix of gas and air. Too much draft can blow it out; too little air can cause a weak, lazy flame that doesn’t properly heat the thermocouple.
Dust, lint, and debris around the burner compartment can also disrupt combustion. Even small changes—like a new exhaust fan, a door that’s now kept closed, or a cluttered utility closet—can affect how air moves around the appliance.
Common causes of a pilot light that keeps going out
1) A dirty pilot orifice or pilot tube
The pilot orifice is a tiny opening that meters gas to the pilot burner. Because it’s small, it doesn’t take much dust or residue to partially block it. When that happens, the flame may look weak, flicker, or burn yellow instead of crisp blue.
A partially clogged orifice can also make the pilot flame “wander” away from the thermocouple. The pilot might light, but it won’t heat the sensor consistently—so it goes out later, often when the main burner cycles on or off.
If you’re comfortable with basic maintenance, you can sometimes clean around the pilot area with a soft brush and compressed air (used carefully and sparingly). If the pilot assembly needs disassembly to clean the orifice, it’s usually better handled by a technician to avoid damaging delicate parts or creating leaks.
2) Thermocouple problems (dirty, worn, or misaligned)
A thermocouple tip should sit directly in the pilot flame. If it’s bent out of position, the flame may not heat it enough. In other cases, the thermocouple simply wears out over time. They’re inexpensive parts, but the diagnosis matters—because a failing thermocouple can look like other issues.
Sometimes the thermocouple is fine, but the connection at the gas valve is loose. A gentle snug (not over-tightening) can help, but if you’re unsure, it’s safer to leave it alone. Stripping threads or cracking the gas valve body can turn a small repair into a big one.
One practical clue: if the pilot lights while you hold the knob down but goes out the moment you release it, the thermocouple circuit is a prime suspect.
3) Downdrafts and ventilation changes
Water heaters and furnaces rely on proper venting to carry combustion gases out of the home. If a downdraft pushes air back down the vent, it can disrupt the pilot flame or even extinguish it. Windy conditions can make this worse, especially if the vent cap is damaged or improperly installed.
Ventilation changes inside the home can also create negative pressure. For example, running a powerful range hood, bathroom fan, or clothes dryer can pull air from wherever it can—including down a chimney or vent—especially in tighter homes.
If your pilot goes out when certain fans run, or only on windy days, that pattern is important. It points toward airflow and venting rather than just a dirty pilot.
4) Low gas pressure or intermittent gas supply issues
Gas appliances are designed for a specific supply pressure. If pressure is too low, the pilot flame may be too small to stay stable or to keep the thermocouple hot. Low pressure can come from issues at the regulator, the gas meter, undersized piping, or high demand when multiple appliances run at once.
Intermittent supply problems can be tricky because the pilot may behave normally for hours or days before failing. If you notice other gas appliances acting odd—like burners that seem weaker than usual—that’s a clue worth sharing with a technician.
Gas pressure testing is not a DIY task. It requires proper tools and knowledge, and it’s a key moment where a professional diagnosis saves time and keeps things safe.
5) A faulty gas control valve
The gas control valve is the “brain” that manages pilot flow and main burner operation. If it’s failing, it may not hold the pilot open even when the thermocouple signal is strong. Sometimes the internal magnet or safety mechanism becomes unreliable.
Because control valves are safety-critical, replacement should be done by a qualified technician. It’s also important to match the correct part and verify proper operation after installation.
If you’ve already addressed the obvious issues—clean pilot, good flame, thermocouple aligned—and the pilot still won’t stay lit, the control valve moves higher on the suspect list.
6) Overheating or high-limit trips (less common, but real)
Some appliances have safety limits that shut things down if temperatures get too high. Overheating can be caused by restricted airflow, a blocked filter (in furnaces), scale buildup (in water heaters), or venting issues.
When a safety trips, it can interrupt operation and sometimes contribute to pilot problems depending on the system design. You might notice the appliance gets unusually hot to the touch or behaves erratically during long run cycles.
This category is a strong “call a pro” signal because overheating and venting problems can involve carbon monoxide risks.
What you can safely observe (without taking the unit apart)
Look at the pilot flame color and shape
A healthy pilot flame is typically steady and mostly blue, often with a small yellow tip. It should wrap around the thermocouple tip. If the flame is weak, flickering, mostly yellow, or lifting off the burner, something is off—usually airflow, dirt, or gas pressure.
If the flame seems to “dance” when the main burner turns on, that can also indicate airflow turbulence or a dirty burner area. Noting these details helps a technician diagnose faster, and it helps you avoid random trial-and-error.
Listen for changes when the main burner engages
When the main burner fires, you may hear a smooth whoosh. A loud bang, delayed ignition, or fluttering can indicate burner or airflow issues that can also affect the pilot.
If the pilot goes out specifically during burner ignition or shutdown, that timing can be meaningful. It may suggest a draft, pressure fluctuation, or dirty burner components.
Check the area around the appliance for drafts and blockage
Without touching the gas components, you can check whether a nearby door slams shut when fans run, or whether air seems to rush toward the appliance room. You can also look for obvious blockages around the combustion air openings (like boxes, paint cans, or piled laundry).
For atmospherically vented appliances, adequate combustion air is crucial. A cramped closet with a solid door and no makeup air can create a starved flame that struggles to stay lit.
Relighting a pilot: the careful, low-drama way
Follow the appliance label exactly
Most water heaters and furnaces have lighting instructions printed on the unit. Those steps are there for a reason, and they often include required wait times to clear gas. If your unit’s label is missing or unreadable, look up the manufacturer’s manual by model number rather than guessing.
When relighting, keep your face and hands clear of the burner opening. Use the built-in igniter if the unit has one. If it requires a match or lighter, consider that a sign to be extra cautious—and if you’re uneasy, it’s completely reasonable to stop and call a technician.
Hold the control knob long enough (but don’t force it)
Many systems require you to hold the pilot knob down for 30–60 seconds (sometimes longer) so the thermocouple heats up. If you release too soon, the pilot can go out even if everything is functioning properly.
If the knob won’t depress smoothly or feels sticky, don’t force it. Mechanical problems in the gas valve are not a DIY fix.
If it goes out again quickly, pause and reassess
Repeated relighting attempts can be frustrating, but it’s better to slow down than to keep cycling gas on and off. If the pilot won’t stay lit after a couple of tries, that’s your cue to switch from “trying” to “diagnosing.”
At that point, the most useful thing you can do is observe: flame color, timing, any drafts, and whether other appliances are acting unusual.
When the problem is really venting (and why it’s not just a comfort issue)
Backdrafting can extinguish pilots and create indoor air hazards
If combustion gases can’t vent properly, they may spill back into the room. That can destabilize the pilot flame and, more importantly, it can introduce carbon monoxide into your living space.
Signs that point toward venting trouble include soot marks, melted plastic near the draft hood, condensation on vent pipes, or a pilot that goes out during windy weather. These aren’t “wait and see” symptoms.
If you suspect backdrafting, stop using the appliance and get it evaluated. A technician may check vent sizing, slope, chimney condition, and whether the home has adequate makeup air.
Tight homes and powerful fans can change everything
Home upgrades like better windows, weatherstripping, and insulation are great—but they can reduce natural air leakage. If you combine that with strong exhaust fans, you can create negative pressure that competes with natural draft venting.
This doesn’t mean you shouldn’t upgrade your home. It just means combustion appliances need to be considered as part of the whole house system. Sometimes the fix is as simple as adding proper combustion air provisions or adjusting venting.
If your pilot issues started after a remodel or new appliance installation, mention that history when you call for service.
Water heater-specific clues that narrow down the cause
Dirty burner compartments and lint buildup
Water heaters often live in garages, utility rooms, or closets—places where dust and lint collect. If the burner compartment is pulling in lint (especially near laundry areas), the pilot can become unstable or the burner can run less efficiently.
You might notice more frequent pilot outages during seasons when you run the dryer more often, or after sweeping and stirring up dust. Keeping the surrounding area clean helps, but internal cleaning should be done carefully to avoid damaging components.
If you see scorch marks, heavy soot, or a strong burnt smell, stop and call a professional. Those are signs that combustion isn’t happening correctly.
Flame arrestor screens and restricted airflow
Many newer water heaters have flame arrestor screens designed to prevent ignition of flammable vapors. Over time, these screens can clog with dust, restricting airflow and causing performance issues—including pilot outages.
Some models allow for cleaning the screen from the outside with a brush or vacuum, but the method varies by manufacturer. Using the wrong technique can damage the screen or push debris into the burner area.
If your water heater has a sealed burner chamber, it’s often best to have a technician handle cleaning and verification.
Furnace-specific clues that point to the right fix
Older standing-pilot furnaces vs. electronic ignition
If your furnace has a standing pilot, the troubleshooting looks a lot like a water heater: thermocouple, pilot cleanliness, and drafts. But many furnaces use intermittent pilot or hot surface ignition, where “pilot problems” are really ignition or flame-sensing problems.
If you’re not sure which type you have, look for a small viewing window and a control board with diagnostic LEDs. A flashing code can be incredibly helpful for a technician—and it can keep you from chasing the wrong issue.
Either way, if you’re seeing repeated shutdowns, it’s worth getting the system serviced before peak heating season so you’re not stuck without heat on the coldest night.
Filters and airflow still matter
Even though filters don’t directly control the pilot, restricted airflow can cause overheating and safety trips that shut down the furnace. If your furnace is short-cycling or shutting off after running a while, check that the filter is clean and that supply/return vents aren’t blocked.
This is one of the few homeowner-friendly checks that can genuinely prevent bigger issues. A $15 filter can save a lot of stress.
If changing the filter improves performance but doesn’t solve the pilot/ignition issue entirely, you may have multiple contributing factors—which is common in older systems.
What not to do (even if a video makes it look easy)
Don’t enlarge or “poke” the pilot orifice
It’s tempting to use a pin or wire to clear a clogged orifice. The risk is that you can damage or enlarge the opening, changing the gas flow rate and creating an unsafe flame.
Proper cleaning uses the right tools and techniques to avoid altering the part. When in doubt, replacement is often safer than improvisation.
If you’ve already tried to poke it and the flame looks worse, stop and call a technician—don’t keep experimenting.
Don’t ignore repeated outages
A pilot that goes out once might be a fluke—like a brief downdraft. But if it’s happening repeatedly, it’s a pattern. Patterns are how appliances tell you something is changing: airflow, venting, component wear, or gas supply.
Repeated outages can also lead to repeated relighting attempts, which increases the chance of unsafe conditions. It’s better to treat it as a real maintenance issue early.
If you’re renting, report it promptly. If you own, schedule service before it becomes an emergency call.
When it’s time to bring in a pro (and how to make the visit more productive)
Situations that deserve a service call right away
Call a professional if you smell gas, see soot, suspect backdrafting, or the pilot won’t stay lit after a couple of careful attempts. Also call if the appliance is very old and you’re unsure about the condition of the venting or gas controls.
In some cases, you may specifically want a licensed plumber or HVAC technician depending on the appliance. For a water heater or gas piping concern, many homeowners prefer to work with a plumber experienced in gas appliances. If you happen to be searching for a local plumber in Phoenix, choose someone who will check combustion safety and venting—not just swap parts.
A good service visit isn’t only about getting the pilot lit today; it’s about making sure it stays lit safely next week and next season.
What to tell the technician (it really helps)
Before the appointment, jot down what you observed: when the pilot goes out (immediately vs. after the burner runs), flame color, whether it happens on windy days, and whether fans or dryers were running. Also note any recent changes like a remodel, new exhaust fan, or a new appliance.
If your unit has diagnostic lights or error codes, write those down too. A photo of the code pattern can be handy.
This kind of detail can shorten diagnostic time and reduce the chances of unnecessary part swapping.
Preventing future pilot problems with small habits
Keep the area clean and breathable
A simple, often overlooked step is keeping the space around the appliance clear. Avoid storing paint, solvents, or dusty items nearby, and don’t block combustion air openings. If your water heater is near a laundry area, be extra mindful about lint.
Light housekeeping can reduce the amount of debris that gets pulled into burner compartments. It won’t fix a failing thermocouple, but it can prevent airflow-related flame issues.
If you vacuum near the appliance, don’t bump gas lines or controls. Gentle is the name of the game.
Schedule periodic maintenance (especially for older units)
Standing-pilot appliances benefit from occasional inspection: checking the pilot flame, cleaning burner components, verifying venting, and confirming safe operation. Think of it like an annual checkup that catches small issues before they become repetitive outages.
Maintenance is also a good time to discuss upgrades. If your unit is nearing the end of its life, a modern replacement with electronic ignition can eliminate standing-pilot hassles and improve efficiency.
Even if you’re not ready to replace anything, knowing the condition of key components helps you plan instead of reacting.
Install carbon monoxide alarms and keep them functional
Carbon monoxide alarms are a must for homes with gas appliances. Install them according to local guidelines (often near sleeping areas) and test them regularly. Replace batteries on schedule and replace the alarm unit when it reaches end-of-life.
While a CO alarm doesn’t prevent pilot problems, it adds a crucial layer of safety if venting or combustion issues develop.
If an alarm ever sounds, treat it seriously: ventilate, evacuate if needed, and get the source checked before using the appliance again.
A quick troubleshooting map you can use in real life
If the pilot won’t light at all
First, confirm the gas control is set correctly and that the appliance has gas supply. If other gas appliances are working, supply is likely present, but the appliance could still have a localized issue.
If you don’t hear or smell any gas at the pilot (and you’re following the lighting procedure), the control valve or supply to the pilot could be the issue. That’s typically professional territory.
If you do smell gas but it won’t ignite, stop and ventilate. Don’t keep trying—something isn’t right.
If the pilot lights but goes out when you release the knob
This often points to the thermocouple not being heated enough, being dirty, misaligned, or failing. It can also be a weak pilot flame that isn’t contacting the thermocouple properly.
Double-check you held the knob down long enough per the instructions. If you did, and it still drops out, it’s time for service.
Try not to “hold it longer and longer” beyond what’s recommended. If the system is healthy, it shouldn’t require heroic effort.
If it runs for hours or days and then goes out
Intermittent outages often involve drafts, venting, negative pressure, or borderline component failure. Note the conditions when it happens: weather, fans, other appliances running, time of day.
Because intermittent issues can be hard to catch in the moment, your observations become even more valuable. A technician can test venting and combustion under different operating conditions.
If the problem is seasonal—like only during windy months—that’s another strong hint toward venting and airflow dynamics.
Pilot lights can be simple, but the reasons they go out aren’t always obvious. By focusing on safe observations—flame quality, timing, and airflow patterns—you can often narrow down the likely cause without taking risks. And when the signs point to venting, gas pressure, or failing controls, bringing in a qualified pro is the fastest path back to reliable, safe heat and hot water.
