BoilerFaultCodesThe 6 most common faults
Your boiler has tried to start up but cannot light the gas to create a flame.
Why it happens: This fault occurs when the boiler's control system attempts to start the combustion process but fails to detect a flame after several attempts. It is usually caused by a lack of gas supply, a worn-out ignition spark electrode that can no longer create a spark, or a faulty gas valve that isn't opening correctly.
Check that your gas supply is turned on at the meter.If you have a prepaid gas meter, check that you have remaining credit.Press the Reset button for two seconds to see if the boiler restarts.
Your boiler has shut down because it has detected an internal temperature that is too high, often caused by a blockage or a pump failure.
Why it happens: This fault occurs when the water inside the boiler gets too hot, causing the safety sensor to trip and shut the system down to prevent damage. The most common reasons are a broken circulation pump that isn't moving the water away from the burner quickly enough, or a build-up of sludge and debris creating a blockage in the heat exchanger.
Check that your radiator valves are open and not turned to zero.Verify that the boiler pressure is between 1 and 2 bar.Press the 'Reset' button on the control panel to see if the fault clears.
Your boiler is shutting down because the water is not circulating properly through the system, causing the heat to build up too quickly in one area.
Why it happens: This fault occurs when water is unable to move through the boiler fast enough to carry heat away, causing a dangerous temperature gap between the outgoing and incoming pipes. The most common reasons are a failing internal pump, a build-up of sludge blocking the pipework, or air trapped within the heat exchanger. Essentially, the boiler is producing heat but has nowhere to send it, so it shuts down to prevent internal damage.
Check that all radiator valves are fully openEnsure there is enough water pressure in the system (typically 1.0 to 1.5 bar)Bleed all radiators to remove trapped air that might be blocking circulation
Your boiler has detected that the water pressure is too low for the system to run safely and has shut down as a precaution.
Why it happens: This fault occurs when the water inside your central heating system drops below the minimum level required for the boiler to operate. The most common reasons are a small leak somewhere in your radiators or pipework, or air being released from the system after the radiators have been bled. Without enough water pressure, the boiler shuts down to prevent the internal heat exchanger from overheating.
Locate the external filling loop (usually a silver flexible hose) under or near the boiler.Slowly open the small valves at each end of the hose until you hear water flowing.Watch the pressure gauge and close the valves once the needle reaches between 1.0 and 1.5 bar.
Your boiler has detected that water is returning much colder than it left, usually because it isn't moving through your radiators properly.
Why it happens: This fault occurs when the water isn't flowing through your heating system fast enough, causing a large temperature gap between the outgoing and incoming pipes. The most common reasons are a failing internal pump that can't push the water around or a blockage in the system, such as a build-up of sludge or a closed valve. When the boiler detects this imbalance, it shuts down to prevent the heat exchanger from overheating.
Check that all radiator valves (TRVs) are fully openEnsure your central heating pump is running and hasn't seizedBleed all radiators to remove trapped air that might be blocking water flow
Your boiler has sensed that the water inside is Getting too hot and has shut itself down as a safety precaution.
Why it happens: This fault occurs when the water leaving the boiler exceeds a safe temperature limit because it isn't moving away quickly enough. The most common reasons are a pump failure that stops water circulation, a blockage in the pipework, or a sensor that is incorrectly reporting the temperature.
Check that all radiator valves are fully open to allow water to circulateEnsure your system pressure is between 1.0 and 1.5 bar on the gaugePress the 'Reset' button for two seconds and release
on the Remeha Avanta 18V
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 Remeha 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