18 High

Boiler Fault Code 18

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 18 appears across 12 boiler brands and 40 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's control panel and its main computer are having trouble communicating with each other, meaning you cannot change settings or see the boiler's status correctly. (As reported on Glow-worm 30ci Plus)

Pick your boiler brand for the 18 fix

Alpha 18 1 model Atag 18 1 model Biasi 18 4 models Chaffoteaux 18 6 models Ferroli 18 3 models Glow-worm 18 4 models Ideal 18 2 models Remeha 18 3 models Saunier Duval 18 4 models Viessmann 18 9 models Vokera 18 1 model Worcester Bosch 18 2 models

Source

Information for the 18 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 27 April 2026