BoilerFaultCodesWorcester Bosch Fault 53 / 125 Fault Code
Also written as FAULT53125 — same fault.
The Worcester Bosch Fault 53 / 125 fault code means: your boiler has detected that a temperature sensor is installed in the wrong place, meaning the system cannot accurately monitor the heat coming from your solar panels or heating circuit.. It appears on 2 Worcester Bosch models in our database.
Technical description: Temperature sensor fitted in wrong location: Collector temperature sensor (T1) fitted on collector array inlet.
What causes the Worcester Bosch Fault 53 / 125 fault?
This fault occurs when the boiler's control system detects that a temperature sensor has been installed on the wrong pipe, specifically the inlet instead of the outlet of your solar panels. Because the sensor is in the wrong place, the boiler receives incorrect data about how much heat is being generated, causing it to shut down for safety. The most common reason is a mistake during the initial installation or the sensor becoming loose and being reattached to the wrong location.
This fault is often first noticed during the spring and summer months when solar panels are actively contributing significant heat to the system.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the Fault 53 / 125 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Fault 53 / 125 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