Pilot stays lit, main burner shuts off early
You hear ignition, the burner lights normally, then drops out before the tank is fully heated while the pilot remains on.
Start here: Start with venting, draft hood behavior, and burner flame appearance.
Gas water heater troubleshooting
Water Heater Burner Not Staying On
Direct answer: When a water heater burner lights and then won’t stay on, the most common causes are a weak pilot flame, dirty burner area, blocked venting, or a failing flame-sensing safety circuit in the gas control assembly. Start with visible vent and flame checks, not parts.
Most likely: On a standard tank gas water heater, a burner that runs for a short time and drops out usually points to poor combustion air, vent spillage, or a pilot/thermocouple style flame-hold problem rather than a bad tank.
First separate the failure pattern: does the pilot stay lit but the main burner shuts off, or does the whole flame go out? That split matters. Reality check: a burner that quits after a minute or two is often reacting to heat or venting, not just a random bad part. Common wrong move: cleaning around the burner with compressed air while the gas is on and the area is still hot.
Don’t start with: Don’t start by buying a gas valve or taking apart sealed gas controls. Those are expensive, fitment-sensitive, and not the first thing to blame.
If you smell gas or see sootShut the control off, ventilate the area, and stop DIY.
If this is a tankless unit going hot then coldUse the tankless symptom path instead of this standing-tank burner guide.
Last reviewed: 2026-04-04
What the burner is actually doing
Pilot and burner both go out
The main burner lights, then everything goes dark and you have to relight the pilot.
Start here: Start with pilot flame strength, thermocouple position, and dirt around the burner assembly.
Burner cycles on for a few seconds at a time
The burner lights, sounds weak or uneven, then cuts off and retries or stays off.
Start here: Start with combustion air openings, burner dirt, and signs of a restricted vent.
Burner only quits when the heater gets hot
It runs longer from a cold start, then starts shutting down sooner on later cycles.
Start here: Start with overheating and vent-spillage clues around the draft hood and top of the tank.
Most likely causes
1. Restricted vent or draft problem
A gas water heater that loses burner flame after it heats up often trips out because exhaust is not moving up the vent properly. You may feel hot air spilling from the draft hood or see scorch marks, moisture, or soot at the top.
Quick check: With the burner running, carefully hold the back of your hand near the draft hood edge without touching metal. Exhaust should pull upward, not roll out into the room.
2. Weak pilot flame or thermocouple not being heated well
If the pilot is small, lazy, or barely touching the thermocouple, the safety circuit may hold for a bit and then drop out once conditions change.
Quick check: Look through the sight window. The pilot should be steady and should wrap the tip of the thermocouple or flame sensor area, not just flicker beside it.
3. Dirty burner or clogged air intake screen
Dust, lint, and pet hair can starve the burner for air and distort the flame. That can cause rollout, weak combustion, or nuisance shutdowns.
Quick check: Check the lower intake area and burner compartment for lint buildup, rust flakes, or a burner flame that looks yellow and soft instead of mostly blue.
4. Failing gas control safety circuit
If venting is good, the burner area is clean, and the pilot flame is strong but the burner still drops out unpredictably, the gas control may not be holding reliably.
Quick check: Only suspect this after the visible airflow and flame checks look normal and the shutdown pattern stays the same.
Step-by-step fix
Step 1: Confirm the exact flame pattern before touching anything
You need to know whether you have a venting problem, a pilot hold problem, or a broader no-heat issue. Those look similar from across the room but lead to different next moves.
- Turn the thermostat setting on the water heater up slightly so it calls for heat.
- Watch through the sight glass from ignition until shutdown.
- Note whether the pilot stays lit after the burner drops out, or whether all flame goes out.
- Listen for any whoosh, fluttering, or repeated clicking if your unit uses electronic ignition.
- Look for soot, scorch marks, melted plastic trim, or moisture around the draft hood and top of the tank.
Next move: If the burner now runs a full heating cycle and the flame stays steady, the issue may have been temporary airflow disturbance or a control setting problem. Keep watching for a repeat. If the burner still shuts off, move to vent and air checks before assuming a failed control.
What to conclude: Pilot-stays-lit points more toward venting, burner quality, or gas control behavior. Pilot-goes-out points more toward pilot flame hold, thermocouple heating, or a safety shutdown.
Stop if:
- You smell gas at any point.
- You see soot, scorching, or flame outside the burner area.
- The burner compartment cover is damaged or missing.
Step 2: Check vent draft and combustion air first
This is the safest high-payoff check. A blocked vent or starved air supply is common, and a water heater can shut the burner down when exhaust or heat builds where it should not.
- Make sure the area around the water heater is not packed with boxes, laundry, paint cans, or anything blocking air movement.
- Inspect the vent connector above the heater for loose joints, sagging sections, rust holes, or obvious blockage.
- With the burner running, feel near the draft hood edge for hot exhaust spilling outward instead of pulling upward.
- Look for lint or dust buildup on any flame-arrestor or intake screen near the bottom of the heater.
- Vacuum loose lint from the outside intake openings only. Do not poke wire or tools into the burner or pilot orifice.
Next move: If clearing the intake area or restoring airflow lets the burner stay on normally, you likely had an air starvation issue. If exhaust spills from the draft hood, the vent path is unsafe or restricted. Stop there and call a pro. If draft looks normal, continue to the pilot and burner inspection.
What to conclude: Good upward draft with a clean intake lowers the odds of a venting shutdown. Spillage, soot, or heavy heat at the draft hood is a strong sign to stop DIY.
Step 3: Inspect the pilot and burner flame quality
Flame shape tells you a lot. A weak pilot or dirty burner can keep the heater running just long enough to fool you before it drops out again.
- Turn the gas control to off and let the burner area cool before opening any access cover allowed by the unit design.
- Check for rust flakes, dust, spider webs, or debris around the burner tray and pilot area.
- Relight only if your label instructions are clear and intact, then watch the pilot flame and burner flame through the viewing area.
- A healthy burner flame is usually steady blue with well-defined flame at the ports. A healthy pilot should directly heat the thermocouple tip.
- If the outside-accessible burner area is dusty, gently vacuum loose debris without bending the pilot tube, thermocouple, or burner parts.
Next move: If the flame becomes steadier after light cleaning around the intake and burner area, monitor it through several cycles before buying anything. If the pilot is still weak, wandering, or not heating the thermocouple well, the burner assembly may need service or the pilot/thermocouple components may be failing.
Step 4: Decide whether this is a pilot-hold issue or a control issue
Once venting and basic cleanliness check out, the next call is whether the safety flame circuit is losing proof or the gas control is dropping out on its own.
- If the pilot goes out with the burner, focus on the pilot flame heating the thermocouple properly and on the condition of the thermocouple connection area if accessible.
- If the pilot stays lit but the main burner drops out early, compare the shutdown timing: immediate, after a minute, or only after the top of the tank gets very hot.
- If shutdown happens only after the heater warms up and you noticed draft hood heat or spillage, treat venting as the primary problem even if the pilot looks decent.
- If the pilot flame is strong and stable, the burner area is clean, and venting appears normal, the gas control assembly becomes more likely.
Next move: If your observations clearly point to one pattern, you can avoid guessing and either replace the supported wear part or call for the right service. If the symptoms are mixed or inconsistent, stop before replacing expensive gas-side parts on a hunch.
Step 5: Take the next safe action based on what you found
At this point the goal is to finish the job cleanly or stop before the repair turns into a gas safety problem.
- If the vent is spilling exhaust, the draft hood is overheating, or you found soot, leave the heater off and schedule professional vent and combustion service.
- If the pilot is weak and does not properly heat the thermocouple, have the pilot/burner assembly serviced and replace the water heater thermocouple if your heater uses a standard replaceable one and access is straightforward.
- If the pilot is strong, the intake and burner area are clean, draft is normal, and the burner still drops out, schedule diagnosis for the gas control rather than guess-buying one.
- If the unit is electric rather than gas, or you actually have no flame at all and no hot water, use the correct no-hot-water path instead of this burner-shutdown guide.
A good result: If the heater completes a full burn cycle and reheats water normally without rollout, soot, or shutdown, keep monitoring over the next day.
If not: If the burner still will not stay on after the safe checks above, stop DIY and get a combustion-qualified water heater tech involved.
What to conclude: A standard thermocouple can be a reasonable DIY repair on some older standing-pilot heaters. Vent faults and gas control faults are the places to slow down and bring in a pro.
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FAQ
Why does my water heater burner light and then go out after a minute?
The first things to suspect are vent draft problems, poor combustion air, or a weak pilot flame that is not keeping the safety circuit satisfied. That timing often points to heat buildup or unstable flame, not just a random bad part.
Can a bad thermocouple cause the burner not to stay on?
Yes, especially on older standing-pilot gas water heaters. If the pilot flame is present but not heating the thermocouple well, or the pilot and burner both drop out, a worn water heater thermocouple is a reasonable suspect after the vent and burner area check out.
Should I replace the gas control valve first?
No. Gas controls are expensive, fitment-sensitive, and not the first thing to blame. Rule out venting trouble, intake blockage, burner dirt, and weak pilot flame first.
What should the flame look like on a gas water heater?
The main burner should usually be mostly blue and steady, not lazy, rolling, or heavily yellow. The pilot should be stable and should directly heat the thermocouple tip or flame-sensing area.
Is it safe to keep relighting a burner that won’t stay on?
Not repeatedly. If you smell gas, see soot, or feel exhaust spilling from the draft hood, stop. A burner that will not stay lit can be warning you about venting or combustion problems, and those are worth taking seriously.
Does this guide apply to tankless water heaters?
Not really. Tankless units that go hot then cold usually follow a different path involving flow rate, scale, sensors, or error codes. Use the tankless symptom path for that pattern.