How much does it cost to fix Ariston error code AA9977?

Typical repair cost for the Ariston AA9977 fault is £250-450 including labour.

AA9977 High

Ariston AA9977 Fault Code

Q: What does the Ariston AA9977 fault code mean?

Your boiler's internal computer is experiencing a communication error and cannot properly monitor its own safety systems.

The Ariston AA9977 fault code means: your boiler's internal computer is experiencing a communication error and cannot properly monitor its own safety systems.. It appears on 4 Ariston models in our database.

Technical description: Problem with the electronic monitoring

Typical repair cost £250-450 (including labour)

Engineer required

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

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Ariston models that show the AA9977 fault code

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

Challenger 80E Repair: £250-450
E-Combi One Repair: £250-450
E-Combi One 30 Repair: £250-450
Microsystem 15 Repair: £250-450

Source

Ariston AA9977 fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026