What does the Atag C1 51 fault code mean?

Your boiler's air circulation system isn't working correctly, which prevents the unit from starting safely so it has shut down to protect your home.

How much does it cost to fix Atag error code C1 51?

Typical repair cost for the Atag C1 51 fault is £250-450 including labour.

fan error (speed control is not achieved or is outside of range)

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.

Sludge build-up — needs flushing, not bleeding.

Safety-critical — turn off, read this.