Common problems guide

The most common Ariston Genus 24 MFFI problems

The faults most likely to send a Ariston Genus 24 MFFI into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.

The 6 most common faults

01

A01 High Engineer

Your boiler has failed to light because it cannot detect a steady gas supply, so it has safely shut down to prevent gas from leaking into your home.

Est. cost: £120-250
Parts: Ignition electrode, Gas valve, PCB

Full guide for A01

02

AA0011 High Engineer

Your boiler has failed to start up because it could not light the internal flame after several attempts.

Est. cost: £120-250
Parts: Ignition electrode, Gas valve, PCB

Full guide for AA0011

03

AA0022 High Engineer

Your boiler is failing to ignite because it cannot detect that the water is warming up after a few attempts, meaning you currently have no heating or hot water.

Est. cost: £150-300
Parts: Ignition electrode, Gas valve, Flame sensor

Full guide for AA0022

04

AA0077 High Engineer

Your boiler is repeatedly failing to stay lit, so it has safely shut down to prevent the release of unburnt gas.

Est. cost: £120-250
Parts: Ignition electrode, Gas valve, Flame rectification probe

Full guide for AA0077

05

AA2211 High Engineer

Your boiler has detected that water is not circulating properly when there is a demand for heat or hot water.

Est. cost: £120-280
Parts: Flow switch, Circulation pump, Diverter valve motor

Full guide for AA2211

06

AA2222 High Engineer

Your boiler is struggling to register that you've turned on a hot water tap, so it isn't starting up to provide hot water or heating.

Est. cost: £120-220
Parts: DHW Flow switch, Microswitch

Full guide for AA2222

Parts most often replaced

on the Ariston Genus 24 MFFI

Ignition electrodeGas valvePCBFlame sensorFlame rectification probeFlow switch

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

You can smell gas or see signs of a leak
The Ariston shows an Emergency or High severity code
The boiler keeps locking out after repeated resets
You've tried the DIY checks and the fault hasn't cleared
There's visible water leaking from the boiler
The flame is yellow or orange instead of blue

See the full 47-code list for the Ariston Genus 24 MFFI