F28
Viessmann
No ignition / gas supply fault
Ignition attempt fails, no flame established, multiple retries then 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
Closed gas cock, Air in gas line after interruption, Low inlet gas pressure, Defective gas valve or ignition sequence
How to Fix / Troubleshooting
Safety: If you smell gas, do not attempt to reset the boiler. Ventilate the area and contact your gas supplier immediately.
- Check gas cock: Confirm that the gas shutoff valve to the boiler is fully open.
- Other appliances: Test another gas appliance (e.g., stove) to confirm gas supply to the property.
- Reset once or twice: After a gas interruption, it may take a couple of ignition attempts to purge air. Press reset once, wait for the cycle, and if necessary, once more.
- Do not keep resetting: If F28 persists after two resets, stop and call a qualified technician to check gas pressure and valve operation.
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Repair Difficulty
Hard
4/5
Required Part
Gas Valve Assembly
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