A.O. Smith Water Heater Pilot/Burner Assembly Replacement

A.O. Smith Water Heater Pilot/Burner Assembly Replacement — What This Part Does

The pilot assembly is the gas-control ignition and sensing assembly that connects the burner to the gas valve. It includes the pilot flame source, ignitor, and thermocouple or thermopile. When you call for heat, the pilot flame allows the main burner to light and heat your water.

Pilot assemblies fail when the ignitor breaks, the thermocouple or thermopile weakens, or the pilot itself becomes clogged or damaged. Air in the gas line, loose wire connections, blocked ventilation, or a worn resistor on older assemblies can also prevent proper operation. When these parts fail, the pilot won’t stay lit or the main burner won’t fire.

Jump to Replacement Steps

Signs It Needs Replacing

• Pilot won’t light or stay lit The pilot flame either never ignites or goes out immediately after you release the control knob.
• Clicking igniter with no flame You hear the igniter sparking but see no pilot flame at the burner assembly.
• No hot water The water heater does not heat water because the main burner cannot fire without a stable pilot flame.
• Pilot flame is yellow or weak The pilot burns with a yellow or orange color instead of a strong blue flame, indicating a clogged or failing pilot.
• Thermocouple or thermopile not generating voltage The sensor at the pilot flame no longer signals the gas valve to keep the pilot open.
• Visible corrosion or damage on pilot bracket or wiring The pilot assembly hardware, wiring, or connectors show rust, breaks, or burn marks.

How to Replace It

1. Turn off the gas supply valve upstream of the water heater and shut off the power to the unit at the breaker or disconnect.
2. Remove the outer burner access cover and disconnect the safety thermostat wires and spark wire from the gas valve.
3. Use the correct wrench to disconnect the pilot gas tube compression fitting from the gas valve, then disconnect the main burner tube and thermocouple or thermopile.
4. Remove the burner and pilot assembly from the tank opening by sliding it out through the front access.
5. Inspect the old pilot assembly for damage and transfer any reusable hardware, then install the new pilot assembly onto the burner bracket, routing the tube and wires through the burner assembly plate.
6. Reinstall the insulator block, burner head, and complete burner assembly back into the tank opening and fasten it in place.
7. Reconnect the compression fitting on the pilot gas tube, the main burner tube, the thermocouple or thermopile leads, the spark wire, and the safety thermostat wires at the gas valve.
8. Restore the gas supply and check all pilot and burner tube connections for leaks using a soap-and-water solution (bubbles indicate a leak).
9. Relight the pilot according to the label instructions on the water heater and verify the main burner fires and the unit heats water.

The Part You Need

Related Error Codes

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

• A O Smith Water Heater E2 error code
• A O Smith Water Heater E4 error code
• A O Smith Water Heater E6 error code

When to Call a Pro

Gas appliance burner and pilot work carries serious risk of gas leak, fire, or carbon monoxide exposure if done incorrectly. If you are not trained in gas-line disconnection, leak testing, and combustion-air requirements, or if you smell gas at any point during this repair, shut off the gas supply immediately and call a licensed plumber or gas technician. Professionals have the tools and knowledge to safely replace pilot and burner assemblies, verify proper combustion, and make sure code-compliant reinstallation. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.