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An igniter heats up to light the gas in your equipment. When it wears out or cracks, the unit may try to start, but the gas will never light.
Specifications
- Part number: 100191120
- Brand: A.O. Smith
- Part type: Igniter
- Dimensions: 23 × 18 × 8 cm
- Height: 0.85 in / 2.16 cm
- Length: 11.6 in / 29.46 cm
- Width: 11.55 in / 29.34 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.
How the Igniter Works
The igniter serves as the heat source that lights the gas burner. When your heating cycle begins, electrical current flows through the element until it gets hot enough to ignite the fuel safely.
Because these parts undergo repeated heating and cooling, they can weaken over time. If the element cracks, electrical current cannot flow through it, leaving your system unable to start a flame.
Dimensions and Physical Measurements
A proper replacement must fit the exact physical space and bracket inside your unit. Check the dimensions of your old part against the listed measurements for number 100191120.
- Dimensions: 23 × 18 × 8 cm
- Height: 0.85 in / 2.16 cm
- Length: 11.6 in / 29.46 cm
- Width: 11.55 in / 29.34 cm
How to Confirm a Match
Never guess when replacing a heating component. To ensure proper operation and safe lighting, verify that every specification aligns with your existing setup.
- Volts: must be the same, often 120 V
- Material: silicon carbide or nitride, as listed
- Shape and mount: must fit the same bracket
Steps for Safe Replacement
If your system tries to start but never lights, a cracked or worn igniter may be the cause. Follow these steps to inspect and replace the part safely.
- Shut off electrical power at the breaker box and close the gas supply valve.
- Take a photo of every wire before removing the old part so you remember where each connects.
- Carefully loosen the mounting screws holding the old assembly in place.
- Remove the old part without bumping surrounding components.
- Position the replacement onto the bracket, handling it only by the base and never touching the element.
- Secure the mount and move wires one at a time to the matching spots on the replacement.
Read your old part
- Wipe away dust from the old part to clearly view its stamp or label.
- Look for the exact part number 100191120 printed on the housing or bracket.
- Check the shape, mounting holes, and electrical connector against your old piece.
- Confirm that the voltage rating matches the requirements of your control system.
When to call a pro
Hire a licensed HVAC technician for any step you are not sure you can do safely. Work that involves opening gas lines, adjusting gas pressure, or running into gas odors always requires professional help.
Questions
Why should I avoid touching the igniter element with bare fingers?
Igniters are brittle and delicate. Skin oil from your fingers can transfer onto the element and shorten its working life.
What happens when an igniter cracks?
If the element is cracked or worn, the system will try to start but will never light the gas. The heating cycle will fail to ignite.
What should I do if I smell gas during the repair?
If you smell gas, do not touch any electrical switch. Leave the house immediately and call your gas company from outside.
Are different voltage igniters interchangeable?
No, they are not interchangeable. Most hot surface igniters run on 120 V, while some use 80 V, so the voltage must match your system.
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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.