BoilerFaultCodesWorcester Bosch Fast flash, Lockout reset: Off Fault Code
Also written as FASTFLASHLOCKOUTRESETOFF — same fault.
The Worcester Bosch Fast flash, Lockout reset: Off fault code means: your boiler has experienced a sudden technical error and has locked itself to prevent damage, requiring a manual reset to attempt to clear the fault.. It appears on 1 Worcester Bosch model in our database.
Technical description: Volatile lockout
What causes the Worcester Bosch Fast flash, Lockout reset: Off fault?
This fault occurs when the boiler's internal computer detects a critical failure during the ignition process or a sudden loss of flame during operation. The most common reasons are worn-out ignition components failing to spark or the gas valve not delivering the correct amount of fuel to the burner.
This fault is slightly more common in winter, as cold weather can put additional strain on aging ignition components and gas valves.
DIY fix possible
Press and hold the 'Reset' button for five secondsWait for the blue light to stop flashing and stay solidCheck if your gas supply is active (e.g. check a gas hob or prepay meter credit)
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Gas Safe Register →Worcester Bosch models that show the Fast flash, Lockout reset: Off fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Fast flash, Lockout reset: Off 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