U9
Worcester
Configuration / Parameter Error
Boiler displays U9, indicating a communication or configuration error, may occur after PCB replacement.
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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
Incorrectly configured Worcester PCB, incompatible control panel, firmware mismatch, wiring error between modules
How to Fix / Troubleshooting
Safety first: Turn off power before accessing electronics.
Homeowner checks:
- Power cycle the boiler and note if the code reappears immediately.
- If the code appeared after recent service or PCB replacement, contact the installer.
Engineer checks:
- Verify that the correct Worcester PCB part number has been installed for the boiler model.
- Enter the installer menu and check configuration parameters (gas type, output, system type) against the data badge.
- Check communication wiring between the main PCB and any additional modules (e.g., pump module, interface).
- Update or reprogram firmware if required by Worcester technical guidance.
This is a specialist configuration issue and should be handled by an engineer familiar with Worcester controls.
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Repair Difficulty
Hard
4/5
Required Part
Main Control PCB
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