BoilerFaultCodesThe 6 most common faults
Your boiler has tried to light but cannot find a flame, which is often caused by a temporary interruption in your gas supply or a blocked flue.
Why it happens: This fault occurs when the boiler's control system attempts to light the burner but fails to detect a steady flame after several attempts. The most common reasons include a temporary interruption in the gas supply, a dirty ignition electrode that can no longer create a spark, or an issue with the air supply preventing successful combustion.
Check that your gas emergency control valve is open and you have credit on your gas meter.Verify if other gas appliances in your home, like a hob, are currently working.Press the 'Reset' button on the boiler control panel to attempt a restart.
Your boiler has reached an unsafe temperature because water isn't circulating properly through the system.
Why it happens: This fault occurs when water cannot travel through the boiler’s internal pipework fast enough to carry away the heat, leading to a build-up of extreme temperature. The most common reasons are a pump that has seized up or internal blockages that are preventing the water from flowing freely through the system.
Wait for the boiler to cool down for at least 20 minutes.Ensure all radiator valves and any internal isolation valves are fully open.Press the Reset button on the control panel to clear the fault.
Your boiler has detected that the water pressure is too low or there is trapped air in the system, preventing it from running safely.
Why it happens: This fault occurs when the internal pressure sensor detects that there isn't enough water in the system to operate safely. The most common reasons are a slow leak in the pipework, air trapped inside the boiler's heat exchanger, or simply needing a top-up after bleeding your radiators.
Locate the filling loop (the flexible silver hose) underneath or near the boiler.Slowly open the valve(s) to let water into the system until the pressure gauge on the boiler reads between 1.0 and 1.5 bar.Close the valves tightly and check if the '04' code has cleared; you may need to press the 'Reset' button.
Your boiler has stopped working because the pipe that carries waste water away is likely blocked or frozen, causing water to back up inside the unit.
Why it happens: This fault occurs when waste water produced during the heating process cannot drain away from the boiler, causing it to back up inside the internal trap. The system detects this rising water level via a sensor and shuts down the boiler to prevent internal flooding or damage. The most common reasons are a blockage in the internal trap or an obstruction in the external pipework leading to a drain.
Check the white plastic pipe outside for ice and pour warm (not boiling) water over it to melt any blockages.Ensure the end of the external pipe is not submerged in a drain or blocked by debris.Restart the boiler using the reset button once the pipe is clear.
Your boiler has detected a blockage or debris in its exhaust system which is preventing waste gases from being safely removed.
Why it happens: This fault occurs when the boiler's internal safety sensors detect that the airflow through the exhaust pipe is restricted or blocked. The most common cause is a build-up of dirt within a small component called the venturi, or a mechanical failure in the fan that prevents harmful waste gases from being pushed out of the property.
Full guide for 03Your boiler's electronic control board has lost its configuration settings or has been set up incorrectly, preventing the system from operating.
Why it happens: This fault occurs when the boiler's central brain, the printed circuit board, cannot identify which specific model of boiler it is supposed to be controlling. It is usually caused by the physical 'jumper tags' on the board being loose, missing, or incorrectly positioned, often following a power surge or a previous repair where the board was replaced. Without these settings, the boiler shuts down as a safety precaution because it doesn't know its own capacity or operating limits.
Full guide for 06on the Vokera Synergy E
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