What does the Atag C1 11 fault code mean?

Your boiler has detected that it is running much hotter than it should be and has switched itself off to prevent internal damage.

How much does it cost to fix Atag error code C1 11?

Typical repair cost for the Atag C1 11 fault is £150-300 including labour.

Maximum temperature exceeded

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Each noise points to a different fault.

Almost always a stuck diverter valve on combis.

Sludge build-up — needs flushing, not bleeding.