Boiler displays E1 256, may not start or may shut down unexpectedly.

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.

Possible Causes

Faulty main PCB, Loose PCB connectors, Internal PCB communication error

Safety first: Isolate power before accessing electronic components. Static precautions should be observed.

Engineer steps:

Inspect all PCB connectors for secure fit and signs of overheating or corrosion; reseat as necessary.
Check supply voltage and earth continuity to the boiler.
If wiring and supply are correct, replace the main control PCB with a genuine Worcester Bosch part and re-commission the boiler.

Hard 4/5

Main Control PCB

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