If a gas water heater won’t light, check gas supply, pilot ignition, flame sensor/thermopile, air intake, and safety switches before calling service.
Cold water and a stubborn burner are frustrating, but you can run safe, smart checks to get the flame back. This guide covers quick diagnostics, safe relighting, status light meanings, and when to stop and call a pro.
Gas Water Heater Pilot Not Lighting — Quick Checks
Start with simple items. Many no-light cases trace back to a closed valve, a tripped thermal switch, a weak pilot, or dust at the air screen.
Fast Symptom-To-Fix Map
| Symptom | Likely Cause | What To Try |
|---|---|---|
| Igniter clicks, no flame | Closed gas valve, air in line, clogged pilot orifice | Verify gas valves inline; hold pilot and spark up to 90 seconds; clear pilot orifice with compressed air |
| Pilot lights, goes out on release | Weak pilot, bad thermocouple/thermopile, loose connectors | Strengthen pilot flame; reseat connectors; replace thermocouple/thermopile if output is low |
| Status light dark | No pilot flame, tripped thermal switch, failed control | Relight pilot; press thermal switch reset; check status code after 60–90 seconds |
| Pilot keeps blowing out | Drafts, venting issues, lifting pilot flame | Eliminate room drafts; verify venting; check pilot flame shape and position |
| Repeated retries, lockout | Ignition fault, sooted pilot, low gas pressure | Clean pilot hood; verify supply pressure; follow lockout clear steps in manual |
| No spark from igniter | Cracked igniter, loose lead | Inspect and replace igniter; reseat lead at control |
| LED blinks multi-flash code | Control reporting a fault | Match blink pattern to the unit’s code chart; act on the listed fix |
Safety First: Gas And CO Precautions
If you smell gas or suspect a leak, do not light the appliance or use switches. Leave the area and contact your gas supplier or emergency services. Manufacturer manuals state this plainly and include shut-off steps in the warnings section.
Add CO alarms near sleeping areas and on each level for extra protection. Keep them tested and powered. Good alarms are not a substitute for proper venting and service when you have combustion problems.
Understand The Ignition Chain
A tank-type gas unit lights a small pilot, the pilot heats a thermocouple or thermopile, that device sends millivolts to the control, and the control opens the main valve when conditions are right. A weak pilot or poor sensing breaks this chain, so the gas valve won’t stay open.
Step-By-Step Relight Procedure (Traditional Pilot)
Prep And Position
- Set the control to “Pilot.” Push and hold the pilot knob.
- Press the igniter once per second while holding the knob. Keep this up for up to 90 seconds; many systems need that warm-up period to wake the status light.
- Look through the viewport for a steady blue pilot. Release the knob slowly. The status LED should begin a normal one-flash cadence after the pilot heats the sensor.
If It Still Won’t Light
- Confirm gas supply: Main house valve open, appliance shutoff inline, and meter running. If the unit was off for service, air in the line can delay the first light. Multiple tries may be needed with the pilot held down.
- Clean the pilot orifice: Dust can choke the flame. Remove the pilot tube and blow out with compressed air. Reassemble, relight, and check flame shape.
- Check the igniter: Inspect for cracks. Verify the spark lead snaps fully into the control and at the igniter tab. If the button feels mushy or there’s no spark, replace the igniter assembly.
When The Flame Won’t Stay Lit
When the pilot dies the instant you release the knob, the control is not seeing adequate millivolts from the sensor. Focus on three things.
Pilot Flame Quality
The pilot should be stable and blue, contacting the thermocouple/thermopile face. If the flame lifts or flickers when the main burner tries to start, the control loses flame sense and shuts down. Clean soot from the pilot hood, correct drafts, and verify gas pressure at the rating plate value.
Thermocouple/Thermopile Output
Loose push-in connectors or a tired thermopile can starve the control. Reseat the connectors and route wires clear of hot surfaces. If output stays low, replace the sensor kit. Many units use kits that include pilot, tubing, igniter, and thermopile for a matched repair.
Tripped Thermal Switch
Combustion chamber overheat opens a one-shot or resettable switch, cutting power to the control. Press the reset button on the switch if your model has one. If it trips again, stop and fix the root cause such as blocked air intake or flame rollout.
Air And Venting: The Hidden Culprits
Newer FVIR-style tanks use a flame arrestor and screened air intake. Lint on the screen starves the burner and pilot. Pull off the base cover, vacuum the screen, and inspect the flame arrestor plate. Also check for room drafts and misaligned baffles that disturb the pilot when the main burner lights.
Status Light And Code Patterns
Controls blink a pattern to point you at the fault. One blink every few seconds is normal; multiple blinks indicate specific issues such as flame failure or sensor faults. Match the pattern to the code chart for your valve model.
Common LED Codes (Guide Only; Check Your Manual)
| Blink Pattern | Meaning | Action |
|---|---|---|
| 1 flash, pause | Normal operation | No action needed |
| 2 flashes | Weak pilot / low sensor output | Strengthen pilot; check thermopile and connectors |
| 3 flashes | Pressure switch / draft issue (power-vent) | Inspect venting and intake; verify fan operation |
| 6-3 sequence | Lost flame after main burner lights | Check pilot lift-off, gas pressure, pilot hood cleanliness |
| Hard lockout | Too many retries | Follow lockout clear steps from the unit manual |
Power-Vent Nuances
Fan-assisted models add a pressure switch and board logic. If there’s no light-off and the fan runs, check the condensate path, vent length, elbows, and terminations. If the control shows a “no light” or “flame lost” code, inspect pilot quality and confirm gas pressure under load.
Drafts, Baffles, And Pilot Lift-Off
A pilot that touches the sensor at idle but lifts when the main flame ignites points to turbulence. Reposition the igniter/sense rod per the service bulletin if your model calls for it, correct baffle placement, and clean carbon from the pilot ground strap. Venting that backdrafts will cause the same symptom.
When You Should Stop And Call A Pro
- Gas odor present, sizzling or roaring sounds, or scorching at the burner door
- Repeated lockouts after proper relight steps
- Damaged wiring, melted connectors, or cracked igniter
- Failed sensor or control replacement on your model requires sealed-chamber access or special test gear
Service techs can measure sensor output in millivolts, check static and dynamic gas pressure, verify vent sizing, and read proprietary code histories on newer controls.
Care And Prevention
Keep The Air Path Clean
Vacuum the intake screen at the base every few months, more often in laundry rooms. A clean air path stabilizes the pilot and shortens light-off.
Annual Burner Check
Pull the burner assembly, brush soot from the pilot hood, and inspect gaskets. Replace brittle rubber seals. Reassemble with correct routing so wires don’t touch hot metal.
Venting And Room Air
Confirm vent slope, joints, and termination are correct. In tight rooms, provide combustion air openings sized per the appliance label. A small louvered door or duct can fix chronic pilot outages from starvation.
Relight Reference
Bookmark the manufacturer’s pilot lighting page for your exact model so you have the correct sequence when you need it.
Model-Specific Notes
- Honeywell/Resideo controls: Normal is single blink. Multi-blink patterns repeat with a pause. The chart in the control’s literature decodes each pattern.
- AO Smith residential tanks: Status light can take up to 90 seconds after pilot ignition to begin blinking; a resettable thermal switch may be present near the combustion door.
- Rheem/UGA-style controls: Tech bulletins reference pilot lift-off fixes and baffle placement checks when you see repeated flame-loss codes.
- Bradford White ICON: The ICON valve uses blink codes to guide troubleshooting; the support page links to model documents and code keys.
Safe Shutdown If Relight Fails
Turn the temperature dial to “Off,” close the appliance gas shutoff, and wait for service. If your unit has electronic display codes, note them before disconnecting power so a tech can get a head start.
Tools And Parts That Save Time
- Compressed air can or small compressor with a nozzle for the pilot orifice
- Vacuum with a brush for the intake screen and chamber
- Fine abrasive pad for light sensor cleanup
- Replacement pilot/thermopile kit matched to your brand
- Manometer and multimeter if you’re trained to use them
Bottom-Line Fix Strategy
- Rule out gas shutoffs and drafty rooms.
- Relight with the correct sequence and allow full warm-up time.
- Clean pilot hood and intake; verify pilot shape on the sensor.
- Reset thermal switch; reseat connectors.
- Replace the sensor kit or call service if codes persist.
Safety link picks: See official pilot relight steps and status light behavior on a major manufacturer’s info page, and review national CO safety guidance. Use brand-specific manuals for code charts and lockout clears.