304
FAULT CODE
ATAG
Too Many Resets
Medium Severity
DIY Check Possible
The boiler has been reset too many times and has entered a protective lockout.
Cold Weather Note
In winter, repeated 133 codes being reset repeatedly will trigger 304. Resolve the condensate issue first.
Step-by-Step Fix Guide
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Step 1
Do NOT press reset again
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Step 2
Turn off at the mains fuse spur for at least 2 minutes
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Step 3
Turn back on
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Step 4
If the boiler locks out again, call a Gas Safe engineer to diagnose the underlying fault
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.