E431
Lennox
Gas Valve / Gas Flow Fault (communicating report)
Thermostat displays E431; furnace may run blower only or shut down after ignition attempt.
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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
Closed manual gas shutoff to Lennox furnace, Faulty gas valve coil, Loose gas valve wiring, Low inlet gas pressure from utility or regulator
How to Fix / Troubleshooting
Danger: Gas work is hazardous. If you smell gas, evacuate and contact the gas utility immediately. Do not attempt repairs.
- 1. Verify gas supply: Ensure the manual gas shutoff valve near the furnace is parallel to the pipe (open). Check that other gas appliances in the home are working.
- 2. Inspect wiring: With power off, verify the gas valve wiring harness is firmly connected and not damaged.
- 3. Reset system: Restore power and call for heat. Observe if the ignitor glows and if burners light. If the ignitor glows but no flame appears, shut the system off and call a professional.
Gas valve and pressure diagnostics must be performed by a licensed HVAC technician with proper instruments.
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Repair Difficulty
Professional Required
5/5
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