F53
FAULT CODE
Johnson & Starley
Flue Temperature Sensor Lockout
High Severity
Engineer Required
The flue gas temperature sensor has triggered a lockout due to excessive flue temperatures or a sensor fault.
Step-by-Step Fix Guide
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Step 1
Turn off the boiler
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Step 2 Engineer only
Call a Gas Safe engineer to inspect the flue system and temperature sensor
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.