304 Medium

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 temporarily locked itself for safety.. It appears on 18 Atag models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

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

DIY fix possible

Turn off the power supply to the boiler at the fused spur switchWait for at least 30 secondsTurn the power back on to clear the software lockout

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like 304: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

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 31 August 2026