E03
Main
Flue Fan or Air Pressure Switch Fault
Boiler shows E03 and shuts down, fan may run but burner does 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
Faulty fan assembly, Blocked flue or condensate trap, Defective air pressure switch, Damaged pressure tubing
How to Fix / Troubleshooting
Safety: Switch off power and isolate gas. Do not operate the boiler with suspected flue or fan faults.
- Check flue terminal: From outside, ensure the Main boiler flue terminal is clear of obstructions (ice, leaves, plastic bags). Remove any blockage.
- Inspect condensate pipe: In cold weather, check the external condensate pipe for freezing. If frozen, thaw gently with warm (not boiling) water and lag the pipe to prevent recurrence.
- Listen for fan operation: On a call for heat, listen for the fan starting. No fan noise suggests a fan or PCB supply issue.
- Engineer checks:
- Test the fan motor on the Main boiler for correct voltage supply and rotation.
- Inspect and replace any kinked or split silicone tubes between the fan/venturi and air pressure switch.
- Test the air pressure switch for correct switching at specified pressures; replace if faulty.
- Check the flue system for correct installation, slope, and integrity according to Main installation instructions.
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Repair Difficulty
Professional Required
5/5
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