How much does it cost to fix boiler error code a/1/8?

Typical repair cost for the boiler a/1/8 fault is £120-250 including labour.

a/1/8 High

Boiler Fault Code a/1/8

Also written as A18 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code a/1/8 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's smart controls are confused because two separate controllers are both trying to act as the primary brain of the heating system at the same time. (As reported on Worcester Bosch GB162)

Pick your boiler brand for the a/1/8 fix

Worcester Bosch a/1/8 1 model

Source

Information for the a/1/8 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026