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A flame sensor proves there is a flame in the equipment. When it senses a flame, it allows the unit to keep heating. If there is no signal, the unit shuts the gas off for safety.
Specifications
- Part number: 25957
- Brand: Nieco
- Part type: Flame sensor
- Height: 0.5 In
- Length: 3.3 in / 8.38 cm
- Material: Rubber
- Width: 4.5 In
- Rod length: about the same as your old one
- Mount: same bracket and screw spacing
- Connector: same terminal style
From the maker's and parts sellers' listings for this number. Compare them with the label on your old part.
How the Flame Sensor Works
A flame sensor sits directly in the path of the burner flame. It works by sending a small electrical current through the flame back to the control board to confirm that the burner lit safely.
If the burners light and then go out after 3 to 10 seconds, a dirty or faulty flame sensor is a common cause. Without a steady signal from the sensor, the control board closes the gas valve to prevent unburned gas from building up inside the unit.
Understanding the 25957 Specifications
When you compare your old sensor to the Nieco 25957 part details, check the physical dimensions listed for this number. Matching these specs ensures the part fits inside the mounting area properly.
- Height: 0.5 In
- Length: 3.3 in / 8.38 cm
- Width: 4.5 In
- Material: Rubber
How to Tell if It Failed
A light cleaning fixes many sensors before a replacement is needed. Soot and oxidation can coat the metal rod over time, blocking the flame signal.
Inspect the physical condition of the old part. You should replace the sensor if the rod is bent or worn, or if the white porcelain insulator is cracked.
Safe Removal and Replacement
Always disconnect electrical power and turn off the gas supply before you start. Take a clear photo of the wire connection before you disconnect anything from the old sensor.
Remove the mounting screw holding the bracket in place, then pull the old sensor out. Position the new sensor using the same mounting holes, secure the screw, and reattach the wire to the matching terminal. Move wires one at a time so nothing is connected incorrectly.
Read your old part
- Check the stamped or printed part number on your old part or equipment diagram to confirm it matches 25957.
- Verify that the rod length is about the same as your old one.
- Check the mount to ensure it uses the same bracket and screw spacing.
- Compare the electrical connection to make sure it uses the same terminal style and wire setup.
When to call a pro
If you are not sure you can complete any step safely, or if you suspect an issue with your gas lines or gas valves, stop and call a licensed HVAC technician.
Questions
Why does my burner light and then turn off after a few seconds?
If the burners light and then go out after 3 to 10 seconds, a dirty or failing flame sensor is a common cause. The sensor must confirm the flame quickly, or the system shuts off the gas supply for safety.
Can I clean my old flame sensor instead of replacing it?
Yes, a light cleaning fixes many sensors. However, you should replace the part if the metal rod is bent or worn, or if the white porcelain is cracked.
Can I bypass a flame sensor to keep heat running?
Never bypass a flame sensor. It is a vital safety device designed to stop raw gas from leaking if the flame does not light.
What should I do if I smell gas while checking the sensor?
Do not touch any switch. Leave the building immediately and call your gas company from outside.
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