Can I keep running the equipment with this fault active?

Generally no. Faults on Water heater units are emitted when a sensor, safety, or control circuit is outside its operating envelope. Running through an active fault risks compressor, heater, or control-board damage. Diagnose and clear the fault first.

What part is most commonly replaced for A.O. Smith Water Heater Gas Control Valve Replacement Guide?

The most frequently replaced parts for A.O. Smith Water Heater Gas Control Valve Replacement Guide are listed in the Parts Reference section of this guide with OEM part numbers and typical price ranges. Check the table for direct replacements.

Is A.O. Smith Water Heater Gas Control Valve Replacement Guide a DIY repair or do I need a technician?

Sensor swaps, fan motor replacements, and condenser cleaning are typical DIY-level repairs. Anything involving refrigerant, gas, or high-voltage (>240V) work requires a licensed technician for both safety and code-compliance reasons.

A.O. Smith Water Heater Gas Control Valve Replacement Guide

Q: What does A.O. Smith Water Heater Gas Control Valve Replacement Guide mean?

Pilot won't stay lit, no hot water, or burner shuts down on safety fault. Replacing a failed gas control valve restores thermostat function and normal operation.

Q: How do I fix A.O. Smith Water Heater Gas Control Valve Replacement Guide?

Follow the step-by-step diagnosis below. The most likely fix is identified by checking power, sensor resistance, and control-board signals in order — using a multimeter and the part numbers documented in the parts reference table.

A.O. Smith Water Heater Gas Control Valve Replacement Guide — What This Part Does

The gas control valve on an A.O. Smith gas water heater is a self-powered electronic valve that regulates gas flow to the pilot and main burner. It reads input from the thermocouple or thermopile to prove the pilot flame is lit, then opens to supply gas to the burner based on the thermostat setting. The valve contains internal control logic that manages ignition, flame proving, and temperature regulation.

The valve fails when its internal control circuit stops responding to proper sensor input, when a weak or contaminated thermocouple or thermopile can no longer generate enough millivoltage to hold the valve open, or when gas supply issues or dirty combustion air screens cause repeated safety shutdowns that eventually damage the valve’s electronics. Loose or overtightened thermocouple connections can also crush the contact and reduce voltage below the threshold the valve needs to operate.

Jump to Replacement Steps

Signs It Needs Replacing

Pilot lights but will not stay lit when you release the button The thermocouple or thermopile is not generating enough millivoltage (below 10 mV for thermocouple or 350 mV for thermopile) to signal the valve to stay open, or the valve itself is not responding to proper input.
No hot water and burner does not ignite The gas control valve is not opening to supply gas to the main burner even when the thermostat calls for heat.
Pilot stays lit but main burner shuts down or cycles on safety fault The valve’s internal control logic is detecting a fault condition (often caused by plugged combustion air screens or poor pilot flame quality) and closing the gas supply.
Pilot flame is weak, yellow, or wavering Contamination in the pilot assembly or restricted combustion air (typically from clogged FVIR screens at the base of the tank) prevents a stable pilot flame and proper thermocouple heating.
Gas odor near the heater or audible hissing at the valve A damaged or leaking gas control valve or loose connection at the valve body allows raw gas to escape.
Thermocouple or thermopile tests good but valve still does not open When sensor output is above manufacturer thresholds (10 mV thermocouple or 350 mV thermopile) and gas supply is confirmed, the fault is in the valve assembly itself.

How to Replace It

Turn off the gas supply at the main gas valve feeding the water heater.
Turn the gas control knob on the valve to the OFF position and wait five minutes for any residual gas to clear.
Locate the model and serial number plate on the side of the tank and note the full model number to order the correct replacement gas control valve for your unit.
Disconnect the pilot tube, main burner supply tube, and thermocouple or thermopile lead from the gas control valve (use two wrenches to avoid twisting the valve body).
Use a wrench to unscrew the gas control valve from the tank (some models require partial draining of the tank first if the valve threads into the tank below the water line).
Install the new gas control valve by threading it into the tank hand-tight, then snug with a wrench (do not overtighten).
Reconnect the pilot tube, main burner tube, and thermocouple or thermopile lead to the new valve (finger-tight plus about one-quarter turn on the thermocouple fitting).
Open the main gas supply valve and check all connections for leaks using soapy water or leak-detection solution.
Follow the lighting instructions on the new valve label to relight the pilot and restore burner operation (press and hold the pilot button, ignite the pilot, hold for 30 seconds, then release and turn the knob to the desired temperature setting).

The Part You Need

Part	Notes
A.O. Smith gas control valve / thermostat assembly	Amazon \| Match the valve part number printed on your existing valve body or contact A.O. Smith with your heater model and serial number (found on the rating plate on the tank side) to identify the correct replacement valve for your unit.
Pipe thread sealant rated for gas (yellow PTFE tape or approved gas pipe dope)	Amazon \| Apply to male pipe threads only per manufacturer instructions to seal the valve connection to the tank.

If this part is failing you may also see one of these codes:

When to Call a Pro

Gas control valve replacement on a tank water heater involves working with natural gas or propane supply lines, disconnecting gas fittings, and proving proper combustion after the repair. If you are not trained to work safely with gas appliances, smell gas during the repair, or cannot get the pilot to stay lit and the burner to operate normally after installing the new valve, call a licensed plumber or gas technician. Professional diagnostics are also recommended if you are unsure whether the fault is in the gas valve, thermocouple, thermopile, gas supply, or combustion air path, because misdiagnosis can lead to unnecessary part replacement and continued downtime. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.