A. O. Smith Gas Water Heater Reset Keeps Tripping

The Short Answer: A red reset button on an A. O. Smith gas tank heater is a heat safety, not an on switch. Repeated trips mean something is overheating the burner area: spilling flue gas, a blocked air path or vent, flame rollout, or a failing switch. One reset after fixing an obvious cause is fine. If it trips again, leave the heater off and call a gas technician.

What the button is protecting

A. O. Smith and its sister brands (State, American, Reliance) use more than one kind of heat safety on gas tank heaters, and the label on your heater says which one you have and whether it can be reset:

• A resettable thermal switch on many flammable-vapor-resistant models, with the reset button in its center. A. O. Smith’s service handbook for its residential FVIR gas models (opens in a new tab) says that if the switch has tripped, the technician should check for flammable vapors and make sure the heater has adequate combustion air and proper draft before relighting, and that the air filter and flame arrestor are clean.
• The energy cutoff (ECO) in the gas control, which shuts off gas if the water overheats. On most residential gas controls this is not a button you can press; if it opens, the control is usually replaced.
• Pressure or blocked-vent switches on power-vent models, which stop the burner when the blower or vent is not working. Those show as status-light codes rather than a red button.

If your heater is electric, its red button is on the upper thermostat and works differently; see why you keep having to reset a water heater.

What the timing of the trip tells you

Write down which pattern you see, plus the model and serial number from the rating plate. That saves a diagnostic step on the service call.

What you can check safely

1. Clear the area around the heater. Boxes, laundry, and lint packed around the base can block the air openings on flammable-vapor-resistant heaters. Do not use or store gasoline, solvents, or paint nearby.
2. Look at the vent from the room. On an atmospheric heater, the metal vent pipe should sit firmly on the draft hood on top of the heater and rise toward the chimney. A pipe that has fallen off or sagged is a carbon monoxide hazard; leave the heater off.
3. Look at the outside termination on direct-vent and power-vent models. Snow, leaves, or a nest in the cap can stop the heater. Clear what you can reach from outside without taking anything apart.
4. Reset once. If you found and fixed an obvious cause, let the heater cool and follow the reset and lighting instructions on its label. If it trips again, stop there.

Do not hold, tape, or jumper the button, and do not remove the burner door or inner cover to look inside.

What the technician will check

A gas technician looks for evidence of rollout (scorching or soot at the burner door), checks that the vent drafts properly with the burner running, and confirms the room has enough combustion air for the appliances in it. They inspect the burner and the flame arrestor screen under the tank on flammable-vapor-resistant models, since a screen clogged with lint or dust starves the burner of air. They also check gas pressure against the rating plate and test the switch itself, which can fail on its own.

Related guides cover the same safety from other angles: gas water heater thermal switch keeps tripping, thermal switch won’t reset, and power-vent problems.

Repair or replace

A failed switch, a cleaned air intake, or a corrected vent are repairs. Replacement makes sense when the trips come from damage that is not worth fixing: a rusted-through combustion chamber, water dripping onto the burner from the tank, or a heater near the end of its life that also needs a gas control. Our guide to estimating water heater age helps with that decision.

Frequently Asked Questions

Q: The reset held for a week and then tripped again. Is that still a problem? A: Yes. A switch that trips occasionally is usually reacting to a real but intermittent condition, such as downdrafts in wind, a lint-clogged air intake, or another appliance competing for combustion air. It still needs a diagnosis.

Q: Can I replace the thermal switch myself? A: Replacing it does not fix why it tripped, and a new switch on a heater that is spilling flue gas only hides the danger. Switch replacement and the checks that should go with it are a technician’s job.

Q: Why does the heater trip only when the dryer or range hood runs? A: Exhaust fans and dryers can pull air out of a tight house faster than it is replaced, which can reverse the draft in a water heater’s vent. Tell the technician; the fix is usually more combustion or makeup air, not a new switch.