Common problems guide

The most common Vokera Vision Combi 25C / 30C problems

The faults most likely to send a Vokera Vision Combi 25C / 30C 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.
10 documented codes
6 most common
1 DIY-safe checks
5 engineer needed

The 6 most common faults

01
A04 High DIY-safe

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

What to try first

Locate the external filling loop (a flexible silver hose) underneath the boiler.Open the small black or chrome valve taps attached to the loop until you hear water entering the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone, typically between 1.0 and 1.5 bar.Close both valves tightly and ensure the pressure remains steady.

Est. cost
£80-150
Parts
Filling loop, Pressure relief valve, Pressure transducer
Full guide for A04
02
A01 High Engineer

Your boiler has failed to light the flame needed to heat your home's water, which means both your heating and hot water are currently unavailable.

Est. cost
£120-250
Parts
Ignition electrode, Gas valve, PCB (Printed Circuit Board)
Full guide for A01
03
A02 High Engineer

Your boiler has detected that the water inside the system has become dangerously hot and has safely shut itself down to prevent damage.

Est. cost
£120-250
Parts
Limit thermostat, Primary flow sensor, Pump
Full guide for A02
04
A03 High Engineer

Your boiler has detected that the internal fan responsible for safely exhausting fumes is not rotating correctly or reporting its speed, so it has shut down to keep you safe.

Est. cost
£180-350
Parts
Fan assembly, Wiring harness, PCB
Full guide for A03
05
A07 High Engineer

Your boiler has detected that the water inside the heating system is getting too hot or that the temperature sensors aren't reading correctly, so it has safely shut itself down to prevent damage.

Est. cost
£120-220
Parts
Primary NTC Thermistor, PCB
Full guide for A07
06
A08 High Engineer

Your boiler has detected that the water temperature coming back into the unit is being read incorrectly or is running hotter than it should be, causing the system to stop working safely.

Est. cost
£120-220
Parts
Return NTC Thermistor, Control PCB
Full guide for A08
Parts most often replaced

on the Vokera Vision Combi 25C / 30C

Filling loopPressure relief valvePressure transducerIgnition electrodeGas valvePCB (Printed Circuit Board)

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
See the full 10-code list for the Vokera Vision Combi 25C / 30C

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →