What does the Grant Overheat thermostat fault code mean?

Your boiler has switched itself off because it has become dangerously hot, likely due to a circulation problem or a system blockage.

How much does it cost to fix Grant error code Overheat thermostat?

Typical repair cost for the Grant Overheat thermostat fault is £150-300 including labour.

Automatically switch off the boiler if the heat exchanger exceeds a pre-set temperature of 111°C ± 3°C.

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.

Work through these before the call-out.