How much does it cost to fix Potterton error code B(3)?

Typical repair cost for the Potterton B(3) fault is £90-220 including labour.

B(3) High

Potterton B(3) Fault Code

Q: What does the Potterton B(3) fault code mean?

Your boiler's small starter flame is either too weak or not staying lit, which is preventing the main burner from firing up to provide heat.

Also written as B3 — same fault.

The Potterton B(3) fault code means: your boiler's small starter flame is either too weak or not staying lit, which is preventing the main burner from firing up to provide heat.. It appears on 3 Potterton models in our database.

Technical description: Pilot rate too low.

What causes the Potterton B(3) fault?

This fault occurs when the small pilot flame remains too small or weak to heat the safety sensor properly. The most common reasons are a tiny piece of debris blocking the pilot jet or a failing thermocouple that can no longer detect the heat of the flame, causing the boiler to shut down for safety.

This issue often appears after the boiler has been turned off for the summer, as dust and debris can settle in the pilot assembly during periods of inactivity.

Typical repair cost £90-220 (including labour)

Engineer required

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

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Potterton models that show the B(3) fault code

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

Source

Potterton B(3) fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.

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