How much does it cost to fix Keston error code E 12?

Typical repair cost for the Keston E 12 fault is £150-300 including labour.

E 12 High

Keston E 12 Fault Code

Q: What does the Keston E 12 fault code mean?

Your boiler has detected that it is getting dangerously hot and has shut itself down to prevent damage to the internal system.

Also written as E12 — same fault.

The Keston E 12 fault code means: your boiler has detected that it is getting dangerously hot and has shut itself down to prevent damage to the internal system.. It appears on 3 Keston models in our database.

Technical description: Thermal fuse blown or flue overheat thermostat activated.

Typical repair cost £150-300 (including labour)

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Keston models that show the E 12 fault code

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

Source

Keston E 12 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

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