304 High

Atag 304 Fault Code

The Atag 304 fault code means: your boiler has been manually reset too many times in a short period and has locked itself out as a safety precaution.. It appears on 2 Atag models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Too many resets
Typical repair cost £0-120 (including labour)

DIY fix possible

Turn the boiler power off at the fused spur switch (the wall switch).Wait for at least 30 seconds.Turn the power back on to clear the temporary software lock.

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Atag models that show the 304 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Atag 304 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026