328 High

Worcester Bosch 328 Fault Code

The Worcester Bosch 328 fault code means: your boiler has detected an issue with the quality of the electricity supply coming into your home, meaning it cannot operate safely.. It appears on 18 Worcester Bosch models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Internal error with the mains voltage – frequency may be inconsistent

What causes the Worcester Bosch 328 fault?

This fault occurs when the boiler's control system detects that the electrical supply from your home is unstable or outside of safe operating limits. It is typically caused by a failure in the boiler's main control board sensing the wrong electrical frequency, or external issues like a power surge or a faulty household circuit. Because the boiler requires a precise voltage to run its internal safety components, it will stop working to prevent damage.

This fault can sometimes be more common during stormy weather or high winds, when external power lines are prone to fluctuating or temporary 'dirty' electricity supplies.

Typical repair cost £250-550 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the 328 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch 328 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026