Vokera Vision Common Problems & Fault Codes (2026 Guide)

The 6 most common faults

A04 High DIY-safe

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

What to try first

Locate the filling loop (a flexible metal hose) underneath your boiler or near your airing cupboard.Open the valves on the filling loop slowly to let water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (usually between 1 and 1.5 bar).Close both valves tightly to stop the flow of water.

Est. cost: £80-150
Parts: Pressure relief valve, Expansion vessel, Filling loop

Full guide for A04

A01 High Engineer

Your boiler has failed to light the flame needed to produce heat or hot water, and it has locked itself out for safety.

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

Full guide for A01

A02 High Engineer

Your boiler has detected that it is running too hot and has safely shut itself down to prevent damage.

Est. cost: £120-250
Parts: Limit thermostat, NTC thermistor, Pump

Full guide for A02

A03 High Engineer

Your boiler is struggling to detect that the internal fan, which clears exhaust gases, is spinning correctly.

Est. cost: £150-£250
Parts: Fan assembly, Printed Circuit Board (PCB), Wiring harness

Full guide for A03

A06 High Engineer

Your boiler is temporarily unable to accurately measure the temperature of your water or heating system due to a faulty sensor.

Est. cost: £120-250
Parts: DHW thermistor, Primary flow thermistor

Full guide for A06

A07 High Engineer

Your boiler has temporarily stopped working because it has detected that the water inside is getting much too hot.

Est. cost: £120-250
Parts: Primary thermistor (flow NTC sensor), Automatic bypass valve, Circulating pump

Full guide for A07

Parts most often replaced

on the Vokera Vision

Pressure relief valveExpansion vesselFilling loopIgnition electrodeGas valvePCB

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 Vokera 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

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See the full 13-code list for the Vokera Vision