High
A05 on Ferroli Optimax HE Plus

Your boiler has stopped working because it cannot detect if the fan, which is essential for safely venting exhaust gases, is spinning correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Tachometer signal interrupted for 1 hour or longer

Shared across the Optimax HE Plus range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

A04View →F05View →

All 22 fault codes on the Optimax HE Plus

Seeing a different code? Every code this model can display, in one place.

A01A02A03A04A06A47F07F10F11F12F13F14F15F34F35F37F39F42FHLow system pressureNo burner ignition

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