F7
Saunier Duval
Air Pressure Switch / Flue Safety Fault
Boiler shows F7 and does not start, or stops shortly after fan starts
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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
Defective air pressure switch, Blocked or kinked pressure tubes, Blocked flue or condensate trap, Incorrect fan speed feedback
How to Fix / Troubleshooting
Safety first: Switch off power and gas. Combustion safety devices must not be bypassed.
Steps to check:
- Inspect the flue terminal outside for obstructions and clear if necessary.
- Remove the boiler front cover and locate the air pressure switch and its silicone tubes.
- Check tubes for splits, kinks, or water. Drain any condensate and refit securely.
- Ensure the condensate trap is not blocked and is correctly filled with water.
- Check the electrical connections to the air pressure switch and fan.
- Reset the boiler. If F7 persists, the air pressure switch or fan may require replacement by a qualified engineer.
Warning: Never link out or bypass the air pressure switch. This is a critical safety device.
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Repair Difficulty
Hard
4/5
Required Part
Air Pressure Switch
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