BoilerFaultCodesWorcester Bosch Fault 52 / 124 Fault Code
Also written as FAULT52124 — same fault.
The Worcester Bosch Fault 52 / 124 fault code means: your boiler has detected that its internal temperature sensors are reading heat in the wrong order, causing the system to shut down for safety.. It appears on 2 Worcester Bosch models in our database.
Technical description: Temperature sensors reversed: Temperature sensors (T1 and T2) reversed.
What causes the Worcester Bosch Fault 52 / 124 fault?
This fault occurs when the boiler's control board detects that the water leaving the unit is cooler than the water coming back, which is physically impossible during normal operation. The most common reason is that the internal temperature sensors have either failed or their wiring has become damaged, sending conflicting signals to the computer. In rarer cases, this can happen if the sensors were accidentally swapped during a recent repair or part replacement.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the Fault 52 / 124 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Fault 52 / 124 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026