Common problems guide

The most common Heatline Vizo 24 problems

The faults most likely to send a Heatline Vizo 24 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.
35 documented codes
6 most common
3 DIY-safe checks
3 engineer needed

The 6 most common faults

01
F22 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 silver flexible hose) underneath the boiler.Open the small valve or tap on the loop to allow mains water into the boiler.Monitor the pressure gauge on the front until it reaches 1.5 bar, then turn the valve firmly off.

Est. cost
£80-150
Parts
Filling loop, Pressure relief valve, Pressure sensor
Full guide for F22
02
F24 High DIY-safe

Your boiler is struggling to move water around the system fast enough, likely due to low water pressure or a blockage.

What to try first

Check your boiler pressure gauge; if it is below 1 bar, use the filling loop to top it up to 1.5 barEnsure all radiator valves are fully openTurn the boiler off and back on again to reset the temporary fault

Est. cost
£120-250
Parts
Central heating pump, System filter, Pressure sensor
Full guide for F24
03
F1 High DIY-safe

Your boiler has tried to light several times but has been unable to sustain a flame, meaning you will have no heating or hot water until it is reset.

What to try first

Check if your gas meter has credit or other gas appliances are workingEnsure the gas isolation valve under the boiler is fully openPress and hold the 'Reset' button (the one with the flame symbol) for 2-3 seconds

Est. cost
£100-£280
Parts
Ignition Electrode, Flame Sensing Probe, Gas Valve
Full guide for F1
04
F28 High Engineer

Your boiler is trying to start but the flame is not catching, meaning it cannot provide you with heating or hot water.

Est. cost
£120-250
Parts
Ignition lead, Ignition electrode, Gas valve
Full guide for F28
05
F00 High Engineer

Your boiler has lost the ability to measure the temperature of the water being sent to your radiators, so it has shut down as a precaution to prevent overheating.

Est. cost
£120-220
Parts
NTC flow temperature sensor
Full guide for F00
06
F01 High Engineer

Your boiler has stopped working because a sensor that monitors the water temperature is not sending a signal to the controls, preventing it from heating your home safely.

Est. cost
£120-220
Parts
NTC Return Sensor, Wiring Harness
Full guide for F01
Parts most often replaced

on the Heatline Vizo 24

Filling loopPressure relief valvePressure sensorCentral heating pumpSystem filterIgnition Electrode

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 Heatline 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 35-code list for the Heatline Vizo 24

Related guides

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