BoilerFaultCodesThe 6 most common faults
Your boiler has failed to ignite or stay lit, meaning your heating and hot water have stopped working.
Why it happens: This fault occurs when the boiler's control system cannot confirm that a flame has been successfully established after several attempts. The most common reasons are a worn-out component that senses the flame, a lack of gas reaching the burner, or a build-up of carbon deposits on the ignition parts.
Check if your gas supply is active by testing another gas appliance like a hob.Try resetting the boiler using the 'R' or reset button on the control panel.Ensure your system pressure is between 1.0 and 1.5 bar on the pressure gauge.
Your boiler has stopped working because there is not enough water flowing through the system to keep it running safely.
Why it happens: This fault occurs when the boiler's internal sensors detect that water isn't moving through the unit fast enough to safely carry heat away from the burner. The most common reasons are a failing internal pump that can no longer push the water or a significant blockage within the main heat exchanger. It can also be triggered by a build-up of sludge in the system pipes that restricts overall flow.
Check the pressure gauge on the front of the boiler; if it is below 1.0 bar, top it up using the filling loop.Ensure all radiator valves are fully open to allow water to circulate.Gently bleed air from your radiators using a radiator key.
Your boiler has failed to light the flame, which means it cannot provide any heating or hot water until the issue is resolved.
Why it happens: This fault occurs when the boiler's control system attempts to start the burner but cannot detect a flame after several attempts. The most common reasons are a lack of gas reaching the unit, worn-out spark electrodes that fail to ignite the gas, or a faulty sensor that cannot 'see' the flame even if it has successfully lit.
Check if other gas appliances in your home, like a hob, are working to confirm your gas supply is active.Ensure your gas meter has credit if you use a prepay meter.Press the Reset button on the boiler control panel once to see if the fault clears.
Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Why it happens: This fault occurs when the boiler's internal computer fails to detect a reliable flame during the ignition process. The most common reasons are worn-out sparks that can no longer light the gas, or a dirty sensor that cannot 'see' the flame even after it has started. It can also be caused by a lack of gas reaching the burner due to a faulty valve or a blockage in the air supply.
Full guide for 04Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Why it happens: This fault occurs when the boiler's internal computer fails to detect a reliable flame during the ignition process. The most common reasons are worn-out sparks that can no longer light the gas, or a dirty sensor that cannot 'see' the flame even after it has started. It can also be caused by a lack of gas reaching the burner due to a faulty valve or a blockage in the air supply.
Full guide for 06Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Why it happens: This fault occurs when the boiler's internal computer fails to detect a reliable flame during the ignition process. The most common reasons are worn-out sparks that can no longer light the gas, or a dirty sensor that cannot 'see' the flame even after it has started. It can also be caused by a lack of gas reaching the burner due to a faulty valve or a blockage in the air supply.
Full guide for 08on the Viessmann Vitodens 200-W
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 Viessmann 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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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