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When your water heater calls for heat, the igniter warms up until it glows. It then lights the gas to heat your water. If the igniter wears out or cracks, the unit may try to start but will never light.
Specifications
- Part number: 100112456
- Brand: A.O. Smith
- Part type: Igniter
- Height: 1 in / 2.54 cm
- Length: 1 in / 2.54 cm
- Width: 1 in / 2.54 cm
- Volts: must be the same, often 120 V
- Material: silicon carbide or nitride, as listed
- Shape and mount: must fit the same bracket
From the maker's and parts sellers' listings for this number. Compare them with the label on your old part.
What the Igniter Does
An igniter serves as the heat source to start combustion. When the system calls for heat, electrical power flows to the element.
The element gets hot enough to light the incoming gas safely. If the part is cracked or worn out, the equipment will attempt to start, but the gas will fail to light. This leaves the system unable to produce heat.
Dimensions and Physical Specs
When checking a part, physical measurements help ensure that the component will fit inside the mounting space. The listed measurements for the 100112456 igniter include:
- Height: 1 in / 2.54 cm
- Length: 1 in / 2.54 cm
- Width: 1 in / 2.54 cm
How to Confirm a Match
To make sure this part fits your equipment, check the old component against key matching standards.
Volts must match what your equipment requires, often 120 V. The material must align with requirements, such as silicon carbide or silicon nitride. Silicon nitride igniters last longer than silicon carbide igniters. Finally, the shape and mount must fit the exact same bracket as the original piece.
Signs of Failure and Replacement Steps
A broken igniter often shows visible cracks, breaks, or dark spots on the heating element. You may also hear the equipment try to fire up without any flame appearing.
Handle the replacement carefully to avoid damaging the new part.
- Turn off the electrical power at the breaker and shut off the gas valve.
- Take a photo of every wire before removing the old igniter so you know where each wire connects.
- Carefully remove the mounting screws and take out the old igniter.
- Install the new part without touching the element with your fingers.
- Move wires one at a time to the same spots and secure the mounting bracket.
Read your old part
- Look for the stamped or printed part number on the old igniter body or bracket.
- Confirm that the number reads 100112456.
- Check that the voltage rating matches the old part, often 120 V.
- Verify that the physical shape and mount match your current bracket so it sits properly in the burner area.
When to call a pro
Hire a licensed HVAC technician for any step you are not sure you can do safely. If you suspect gas leaks or need help working around gas lines, stop and call a licensed professional.
Questions
Why should I avoid touching the igniter element?
Igniters are very brittle. Skin oil from your fingers can damage the material and shorten the life of the heating element.
What happens if an igniter fails?
If the igniter is cracked or worn, the equipment tries to start but the gas never lights. The unit will not produce heat until the igniter is replaced.
What should I do if I smell gas during the repair?
Do not touch any electrical switch. Leave the house immediately and call your gas company from outside.
Are different igniter voltages interchangeable?
No, they are not interchangeable. Most furnace hot surface igniters run on 120 V, while some use 80 V, so the voltage must match.
Related part numbers
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Brand names and part numbers identify the part and show fit. HVAC Fitter is not affiliated with, authorized by, or endorsed by any equipment maker. If you are not sure a repair is safe for you, call a licensed HVAC technician.