A.O. Smith gas water heater status light: 1 flash every 3 seconds
Normal operation: the pilot is lit and the gas control valve has not detected any problem. No corrective action is needed. Not a fault.
If you smell gas
Stop: do not relight or troubleshoot anything. A.O. Smith’s own words (Residential Gas Water Heater Installation Instructions and Use & Care Guide 100263112, cover page):
- Do not try to light any appliance.
- Do not touch any electrical switch; do not use any phone in your building.
- Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
- If you cannot reach your gas supplier, call the fire department.
Calling from a neighbor’s phone means leaving the building first.
What you see: one flash, then a pause, repeating. Applies to: A.O. Smith residential atmospheric gas water heaters with the Flammable Vapor Ignition Resistant safety system and an electronic gas control valve. State heaters use the same codes.
What it means
The manual’s wording: “1 FLASH (EVERY 3 SECONDS)” — A.O. Smith and State electronic gas control valve.
Normal operation: the pilot is lit and the gas control valve has not detected any problem. No corrective action is needed.
Not a fault.
What A.O. Smith tells the owner to do
- A.O. Smith says that if the light flashes once every three seconds and you have no hot water, make sure the gas control knob is set to HOT.
semiatic gives no repair instructions of its own. The steps above are only the ones A.O. Smith addresses to the owner in its manual.
When to call a qualified service agency
This pattern is normal operation. If the light shows a fault code instead, or you have no hot water with the light normal and the knob set correctly:
A.O. Smith’s manual: “Installation and service must be performed by a qualified installer, service agency or the gas supplier.” Its Technical Assistance Hotline is 1-800-527-1953; have the model and serial number from the data plate ready.
Source
A.O. Smith’s own manuals, read on the date shown.
- A.O. Smith: Residential Gas Water Heater Installation Instructions and Use & Care Guide (100263112, January 2015), “Status Light Code Troubleshooting Chart” and “Lighting the Pilot” — A.O. Smith residential atmospheric gas water heaters with the Flammable Vapor Ignition Resistant safety system and an electronic gas control valve. assets.hotwater.com Checked 2026-09-29.
- State Water Heaters (A.O. Smith): Residential Standard Gas Water Heater Service Handbook (327306), “Diagnostic Flash Codes” — State residential standard (atmospheric) gas water heaters with the electronic gas control valve/thermostat — a handbook written for qualified service professionals. www.statewaterheaters.com Checked 2026-09-29.
The same pattern on other brands
The same count on another maker’s gas control can mean something else.