BoilerFaultCodesWorcester Bosch Condition K Fault Code
Also written as CONDITIONK — same fault.
The Worcester Bosch Condition K fault code means: your boiler's internal computer brain is failing to communicate correctly, often due to moisture or a significant electronic fault.. It appears on 1 Worcester Bosch model in our database.
Technical description: Light indication during fault not covered by other details. Control board is likely to be wet, damaged, or malfunctioning.
What causes the Worcester Bosch Condition K fault?
This fault occurs when the boiler's main control board suffers a critical internal failure or a loss of signal between components. The most common reason is moisture ingress from a small internal leak or dampness in the air reaching the electronics and short-circuiting the board. In some cases, it can also be triggered by a loose or damaged wiring harness that prevents the boiler's 'brain' from sending instructions to the rest of the unit.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the Condition K fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Condition K 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