AO Smith Gas Water Heater Reset Keeps Tripping

The Short Answer: An AO Smith gas water heater reset that trips repeatedly is reacting to a flame rollout, blocked vent, dirty combustion air path, overheated chamber, or failing gas control. Reset it once only after the unit is cool and the obvious outside cause is gone. If it trips again, leave the gas off and hire a licensed plumber.

Search Intent & The Real Problem

The red reset button on an AO Smith gas control is a safety limit, not an ignition switch. Depending on the model, the button may be the energy-cutoff device in the thermostat, a thermal switch in the combustion-air path, or part of the gas control’s high-limit circuit. A gas water heater can still have a pilot and a status light while that safety has opened.

Do not swap in a thermocouple because a forum said “reset.” A weak pilot signal usually lets the pilot go out; it does not explain a thermal switch that opens after the burner runs. A burner that lights and then trips the reset points toward heat, flame pattern, or venting. A button that trips immediately after a reset needs a technician and should not be held in.

What other guides get wrong

The common advice is to press the button until it stays in. That defeats the exact safety that is telling you the combustion system is unsafe. Other guides confuse AO Smith gas controls with electric-tank thermostats, recommend opening gas fittings, or tell you to clean inside a sealed combustion chamber. A reset is a symptom. The sequence and timing of the trip are the useful information.

Step-by-Step Troubleshooting

Step 1: Record what trips and when

• What to look for: Which button opened, whether the burner was running, and the exact status-light pattern. Photograph the rating plate and control before cycling anything.
• Required tools: Flashlight and phone. No screwdriver is needed for this step.

Step 2: Check the outside air and vent path

• What to look for: On a power-vent model, the blower must start before ignition and the intake and exhaust terminations must be clear. On an atmospheric model, the draft hood and vent connector must be intact, supported, and free of obvious collapse. Snow, leaves, a bird nest, or a termination buried by a remodel can make a good heater trip its safety.
• Required tools: Eyes from outside the cabinet. Do not remove the draft hood or reach into the burner.

Clear snow and leaves from an exterior termination if you can do it without opening the appliance. A blower that hums, starts late, or does not start is a stop point. Do not bypass the pressure switch so the burner can run.

Step 3: Look for evidence of rollout or overheating

• What to look for: Soot above the burner, melted wire insulation, a scorched combustion door, rust at the chamber, or a flame that lifts, rolls out, or burns yellow. Water in the burner tray or a rust ring at the chamber means the tank is failing and must not be fired.
• Required tools: Flashlight only. Keep the gas control off if any of these signs are present.

A normal burner flame is stable and mostly blue. Do not treat a yellow or lifting flame as a burner-adjustment project. Combustion analysis and gas pressure testing belong to a licensed technician.

Step 4: Allow one safe reset only

• What to look for: The heater is cool, there is no gas smell, there is no water in the burner, and the outside vent path is visibly clear. Follow the label on the exact AO Smith control. A single reset may confirm that a temporary outside obstruction cleared.
• Required tools: The appliance label. No jumper wire, magnet, tape, or tool on the safety.

If the button opens again, turn the control to OFF and close the appliance gas cock if you can identify it without forcing anything. Do not restart it for another “test.”

Step 5: Give the technician useful evidence

• What to look for: Model number, serial number, fuel type, status-light count, time until the trip, blower behavior, and any recent rain, wind, outage, or plumbing work.
• Required tools: Phone camera and notes.

Typical appliance gas pressure ranges are model-specific; residential NG may be around 3.5–7 inches water column and LP around 10–11, but the rating plate and installation manual control. Do not connect a manometer or loosen a gas fitting as a homeowner test.

When DIY Ends: Calling a Licensed Pro

DIY ends after one safe reset or as soon as there is soot, rollout evidence, a failed blower, a blocked vent that is not plainly external, water in the chamber, gas odor, or a repeated trip. A licensed plumber can test draft, combustion, gas pressure, the thermal switch circuit, and the AO Smith control without defeating a safety. Repeated resets can turn a warning into fire or carbon monoxide exposure.

Frequently Asked Questions

Q: Why does my AO Smith gas water heater reset button keep tripping? A: The usual causes are blocked venting, poor combustion air, flame rollout, overheating, water in the burner, or a failing safety or gas control. The timing of the trip helps a licensed technician find it.

Q: Can I hold the reset button in to keep the heater running? A: No. Never tape, jumper, or hold a thermal reset or rollout safety. It can expose the room to fire or carbon monoxide. Reset once only under the label’s instructions, then stop if it opens again.

Q: Does a tripping reset mean I need a new water heater? A: Not always. A clear external vent obstruction or failed switch may be repairable. Soot, water in the combustion chamber, a rusted tank, or repeated overheating can make replacement safer. A licensed plumber should separate those cases.