How much does it cost to fix Atag error code A5?

Typical repair cost for the Atag A5 fault is £100-200 including labour.

A5 Low

Atag A5 Fault Code

Q: What does the Atag A5 fault code mean?

Your boiler is struggling to detect the outdoor temperature, but it will continue to heat your home using its internal settings as a backup.

The Atag A5 fault code means: your boiler is struggling to detect the outdoor temperature, but it will continue to heat your home using its internal settings as a backup.. It appears on 2 Atag models in our database.

Technical description: Outside temperature (only if an outside sensor is connected)

Typical repair cost £100-200 (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 A5 fault code

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

A200 Repair: £100-200
Q 25CR Repair: £100-200

Source

Atag A5 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