How much does it cost to fix Ariston error code B03?

Typical repair cost for the Ariston B03 fault is £140-£280 including labour.

B03 High

Ariston B03 Fault Code

Q: What does the Ariston B03 fault code mean?

Your boiler's internal mechanism that controls the flame size has failed, meaning the system cannot regulate its heat output properly and has shut down for safety.

The Ariston B03 fault code means: your boiler's internal mechanism that controls the flame size has failed, meaning the system cannot regulate its heat output properly and has shut down for safety.. It appears on 6 Ariston models in our database.

Technical description: Gas Valve Modulator

Typical repair cost £140-£280 (including labour)

Engineer required

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

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Ariston models that show the B03 fault code

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

Challenger 80E Repair: £150-250
E-Combi One Repair: £150-250
E-Combi One 30 Repair: £150-250
Euro Combi 30 MFFI Repair: £140-£280
Euro Prisma 24 Repair: £180-350
Microsystem 15 Repair: £150-250

Source

Ariston B03 fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.

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