CODE 21
Fraser-Johnston
Gas Heating Lockout
LED flashes two short and one long blink; inducer runs but burners do not light.
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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
Failed gas valve, No 24 VAC to gas valve from IFC, Low inlet gas pressure, Blocked manifold orifices
How to Fix / Troubleshooting
Safety first: Shut off gas and power before working on gas components. Gas pressure and valve testing should be done by a licensed technician.
- Verify ignition sequence: Confirm that the hot surface ignitor glows and that the pressure switch is closing before the gas valve should open.
- Listen for gas valve click: During ignition, listen for a distinct click from the gas valve. No click may indicate no control signal or a failed valve coil.
- Check wiring to gas valve: With power off, ensure the 2‑wire harness to the gas valve is firmly connected and not damaged.
- Professional testing: A technician should measure 24 VAC at the gas valve during ignition and check gas pressure with a manometer. If voltage is present but no gas flows, the valve must be replaced.
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Repair Difficulty
Professional Required
5/5
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