Ao smith water heater gas burner no hot water — gas burner

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   Confirm the symptom without opening the heater. Check hot-water availability at more than one faucet after allowing the system's normal recovery period, and identify whether the water is cold everywhere or only at one fixture. Avoid touching water that may be unexpectedly hot and do not remove any burner or control cover.

   Expected result: All fixtures are cold, one fixture is cold while others have hot water, hot water returns after recovery, or the water is dangerously hot rather than cold.

   Next step: If the symptom is not system-wide, arrange plumbing diagnosis for the affected fixture. If all fixtures are cold, continue only with external, model-approved indicators and keep the heater's safety boundary in view.

   Why this matters

   Why: Cold water at every fixture keeps the heater's ignition, fuel, safety, or control path in scope; a single cold fixture points to local plumbing or mixing hardware. A dangerously hot result is a scalding-control problem, not a reason to increase the heater setting.

2. Check 2

   Identify the exact model, fuel configuration, gas-control type, and status-light or display behavior from the rating label and manual. Observe the pilot and burner only through the designed viewing window or indicator, without removing an inner door, reaching into the combustion area, or disturbing wiring or tubing.

   Expected result: The pilot is lit and the status indicator is normal, the pilot is out, the indicator is dark or flashing an abnormal pattern, or the burner never starts when heat is called for.

   Next step: Record the indicator pattern and model number. Follow only the exact manual's low-risk observation or pilot-lighting instructions; do not guess a fault code or open the burner assembly.

   Why this matters

   Why: The pilot and indicator state select different manual troubleshooting paths. An abnormal status can indicate an electrical, gas-control, thermopile or safety condition; a pilot that is lit but a main burner that never starts needs more than a temperature-dial change.

3. Check 3

   If the pilot is out and there is no gas smell, review the lighting label and exact model manual before attempting any relight. Stop immediately if the pilot will not light as directed, goes out when the control is released, or the heater shows an unexpected status pattern; do not make repeated attempts beyond the manual's procedure.

   Expected result: The pilot lights and remains lit, the pilot will not light, the pilot lights but goes out, or gas odor appears during or after the attempt.

   Next step: For a successful manual-approved relight, observe whether the main burner starts as the manual describes. For a failed relight, recurring dropout, or any gas odor, turn the control to the safe position if the manual allows, leave the area as appropriate, and arrange qualified service.

   Why this matters

   Why: A pilot that remains lit allows the manual's next burner check; a pilot that will not light or will not hold can involve gas supply, ignition, flame-sensing, or a safety control. Gas odor changes the situation to an immediate gas-safety response.

4. Check 4

   With the heater off and cool enough for a visual check, inspect only the accessible air-inlet screen, draft hood, and vent connection for obvious blockage, separation, damage, or objects stored around the heater. Do not remove the draft hood, use smoke or flame to test draft, clean a hidden burner, or modify venting.

   Expected result: An air opening is blocked, the draft hood or vent is loose or damaged, the area is unobstructed, or the thermal or air-supply safety has tripped again.

   Next step: Remove only an obvious object that is safely outside the heater and never block the opening. For a recurring safety trip, damaged or altered vent, soot, abnormal exhaust, or uncertain airflow, stop and arrange qualified gas-appliance service.

   Why this matters

   Why: A. O. Smith links thermal-switch trips with an air-supply problem and requires adequate combustion air and proper venting. A blocked, altered, or damaged vent can create combustion and carbon-monoxide risk; a clear exterior does not prove internal airflow is safe.

5. Check 5

   Check the manual gas shutoff and the gas-control setting only from a safe standing position and only if you are confident identifying them. Do not loosen a gas connection, test pressure, remove a burner, or adjust a regulator. If the home has other gas appliances, note whether they also fail without manipulating their controls.

   Expected result: The heater's shutoff is not in the manual's open position, other gas appliances also fail, the heater alone has no burner, or a gas smell is present.

   Next step: If there is a suspected utility interruption, contact the gas utility or qualified service provider. For heater-only failure, abnormal flame, or any odor, leave gas-component diagnosis and repair to a qualified professional.

   Why this matters

   Why: A closed supply or broader gas interruption may explain a cold tank; a heater-only failure keeps the pilot, thermopile, thermal safety, gas control, or burner path in scope. Gas odor or uncertainty is not a troubleshooting result to work around.

6. Check 6

   After a manual-approved pilot relight or external correction, observe one normal heating call through the viewing area without opening the burner compartment. Note whether the main burner ignites, burns steadily, drops out, or never starts, and stop if flame leaves the intended area or the venting sounds or looks abnormal.

   Expected result: The burner ignites and remains stable, ignites then drops out, never ignites with a lit pilot, or shows soot, unusual flame, noise, or exhaust.

   Next step: Do not relight repeatedly or adjust gas controls. Turn the heater to the safe state described by the manual and arrange qualified service for any unstable, abnormal, or absent burner operation.

   Why this matters

   Why: A stable burner supports a restored ignition sequence, but a burner that drops out or never starts can involve flame sensing, air supply, gas control, or burner condition. Soot, abnormal flame, or exhaust is a combustion-safety concern rather than a homeowner adjustment.

7. Check 7

   Before any restart, verify from the exact manual that the water heater's tank is full, the drain valve and water connections are secure, and no wiring or covers are exposed. Restore operation only through the model's stated sequence, then monitor hot-water recovery without changing the setting to an unsafe level.

   Expected result: The tank cannot be confirmed full, water connections leak, the pilot or burner remains abnormal, the heater recovers normally, or no hot water returns.

   Next step: Do not restore gas operation when the tank is not full, a leak is present, or any gas, flame, vent, or safety abnormality remains. Arrange qualified plumbing or gas-appliance service and provide the recorded indicator pattern.

   Why this matters

   Why: A. O. Smith warns that a heater must be full before operation and that startup safety checks matter. Normal recovery after a manual-approved correction supports an ignition interruption; no recovery or a recurring fault needs diagnosis of the burner, control, gas supply, or another system component.