C10 High

Atag C10 Fault Code

The Atag C10 fault code means: your boiler is confused because two temperature sensors have been incorrectly identified or swapped, preventing it from safely heating your water.. It appears on 1 Atag model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Flow and return sensors exchanged
Typical repair cost £120-220 (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 →

Atag models that show the C10 fault code

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

Source

Atag C10 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.

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