FVS
American Water Heaters
Flammable Vapor Sensor (FVS) Lockout
Flammable vapor ignition resistant (FVIR) gas water heater status light flashes a specific pattern indicating flammable vapor sensor lockout.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Flammable vapors detected near heater, Contaminated or failed flammable vapor sensor, Blocked combustion air intake at base, Spilled chemicals near heater
How to Fix / Troubleshooting
Critical safety warning: If flammable vapors are suspected, ventilate the area immediately and remove ignition sources. Do not operate the heater until the area is safe.
- 1. Remove ignition sources: Extinguish open flames and stop using solvents, gasoline, or paints near the heater.
- 2. Ventilate area: Open doors and windows to disperse vapors.
- 3. Inspect air intake: On FVIR models, check the flame arrestor screen at the base of the heater for lint, dust, or debris. Clean gently with a soft brush and vacuum.
- 4. Check flammable vapor sensor: Locate the sensor near the base pan. Inspect wiring and connector. If the sensor is contaminated or out of resistance range (per manual), replace it.
- 5. Reset control: Some models require a specific reset procedure (cycling the gas control knob and waiting a set time). Follow the installation manual exactly.
- 6. If lockout persists: Contact a qualified technician. Do not bypass or jumper the flammable vapor sensor.
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Repair Difficulty
Hard
4/5
Required Part
Flammable Vapor Sensor
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