How much does it cost to fix Atag error code A1?

Typical repair cost for the Atag A1 fault is £120-250 including labour.

A1 Medium

Atag A1 Fault Code

Q: What does the Atag A1 fault code mean?

Your boiler is struggling because the temperature of the water returning to it from your radiators is not what it expects, which is causing it to pause operations to protect itself.

The Atag A1 fault code means: your boiler is struggling because the temperature of the water returning to it from your radiators is not what it expects, which is causing it to pause operations to protect itself.. It appears on 2 Atag models in our database.

Technical description: Return water temperature

Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Atag models that show the A1 fault code

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

A200 Repair: £120-250
Q 25CR Repair: £120-250

Source

Atag A1 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 27 April 2026