86 High

Atag 86 Fault Code

The Atag 86 fault code means: your boiler has detected that the electricity coming from your home's wall socket is unstable, meaning it cannot operate safely and has shut itself down.. It appears on 3 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: The frequence of the power supply deviates more than 2,5Hz (<47,5Hz, >52,5Hz)
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 86 fault code

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

Source

Atag 86 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