How much does it cost to fix boiler error code Return Thmr Fault?

Typical repair cost for the boiler Return Thmr Fault fault is £120-220 including labour.

Return Thmr Fault High

Boiler Fault Code Return Thmr Fault

Also written as RETURNTHMRFAULT — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 31 August 2026

Fault code Return Thmr Fault appears across 2 boiler brands and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's temperature sensor at the water return pipe is faulty or disconnected, causing the system to stop heating because it cannot accurately measure the water temperature. (As reported on Keston Heat 45)

Pick your boiler brand for the Return Thmr Fault fix

Ideal Return Thmr Fault 1 model Keston Return Thmr Fault 2 models

Source

Information for the Return Thmr Fault fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026