What does the Vaillant F.24 fault code mean?

Your boiler is shutting down because it is heating up much faster than it is moving the water around, which often points to a circulation problem.

How much does it cost to fix Vaillant error code F.24?

Typical repair cost for the Vaillant F.24 fault is £150-350 including labour.

Safety switch-off: Temperature rise too fast

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.

Almost always a stuck diverter valve on combis.