A.O. Smith 100108267 Thermocouple

How the Thermocouple Protects Your Water Heater

A thermocouple is designed to sense the heat from a standing pilot flame. When the pilot is lit, the tip of the thermocouple heats up and generates a tiny millivolt (mV) electrical signal.

The gas valve senses this tiny voltage and holds its internal safety magnet open. As long as the pilot flame stays lit, gas continues to flow safely. If the pilot goes out, the thermocouple cools down immediately. Without that small voltage, the gas valve closes shut automatically for safety.

Understanding the 100108267 Specifications

When you check a replacement part, reviewing the listed physical measurements helps you make sure it will fit the space in your burner assembly. The listed specs for part 100108267 are:

• Height: 0.95 in / 2.41 cm
• Length: 4.95 in / 12.57 cm
• Width: 3.45 in / 8.76 cm

How to Confirm a Match

To make sure this part fits your equipment, compare your old piece against the listed type and size. The replacement must be a thermocouple (mV) or thermopile, exactly as listed for your setup.

Check the length to confirm it is the same or a little longer than the original piece. A piece that is too short will not reach the pilot bracket. You must also check the fitting at the gas valve to verify it uses the same nut or terminals as your existing hardware.

Signs of Failure and Replacement Steps

A common sign of a bad thermocouple is a pilot light that will not stay lit. If the pilot lights while you hold down the pilot button, but goes out as soon as you let go, the thermocouple is often the cause of the problem.

Always follow standard safety procedures if you decide to service the part yourself:

1. Turn off the main gas supply line to the water heater.
2. Take a clear photo of the burner setup and connections before taking anything apart.
3. Carefully remove the old thermocouple from the pilot assembly and disconnect the fitting at the gas control valve.
4. Secure the new thermocouple into the pilot bracket so the tip sits properly in the pilot flame path.
5. Thread the nut or connector into the gas valve, moving carefully to match the original setup.

Read your old part

1. Turn off the gas and allow the burner assembly to cool completely.
2. Look for part number 100108267 stamped or printed directly on the old part, its tag, or in your equipment documentation.
3. Check that the replacement is a thermocouple (mV) or thermopile, as listed for your heater.
4. Verify the physical dimensions, including the length of 4.95 in / 12.57 cm, to ensure it reaches properly.
5. Examine the fitting at the control valve end to confirm it matches the same nut or terminals.