BoilerFaultCodesThe 6 most common faults
Your boiler is failing to light the burner, meaning it cannot provide you with any heating or hot water.
Why it happens: This fault occurs when the boiler's control system attempts to start a flame but fails to detect one after several tries. It is often caused by a lack of gas reaching the burner, a worn-out spark electrode that can no longer create a light, or a dirty sensor that cannot 'see' the flame once it has started.
Check if other gas appliances, like a cooker, are working to ensure gas is reaching the propertyCheck if your gas meter has creditPress the reset button on the boiler control panel
Your boiler has switched itself off because it has detected dangerously high temperatures, likely caused by a disruption in the flow of water circulating through your radiators.
Why it happens: This fault occurs when the water inside the boiler gets too hot too quickly, triggering a safety sensor to shut the system down. The most common reasons are a pump failure that prevents water from moving, or a blockage caused by sludge and debris trapped inside the main heat exchanger.
Check that all radiator valves are fully open to allow water to circulate.Ensure there is enough water pressure in the system (typically 1.0 to 1.5 bar).Press and hold the reset button for 2-5 seconds to see if the system restarts.
Your boiler has locked itself for safety after too many unsuccessful restart attempts in a short period of time.
Why it happens: This fault occurs when the boiler's safety software detects too many manual reset attempts in a 15-minute window and enters a protective lockout. It is usually triggered because an underlying issue caused the boiler to fail initially, leading the user to repeatedly press the reset button. The boiler essentially stops responding to prevent potential damage or further safety risks from constant restarting.
Turn the boiler power off at the fused spur switch (the wall switch).Wait for at least 15 to 30 minutes to allow the internal timer to clear.Turn the power back on and see if the fault has cleared, but do not press reset again if a different fault code appears.
Your boiler is struggling to detect the temperature of the water being heated for your taps, which means it has safely shut down to prevent overheating.
Why it happens: This fault occurs when the electrical voltage entering the boiler drops below the minimum level required for its electronic components to function correctly. The most common reason is an instability in your home's mains power supply or a loose connection within the boiler's internal wiring that is restricting the flow of electricity. In some cases, the boiler's main control board may be incorrectly detecting a drop in power due to a failing internal sensor.
Check if other appliances in your home are struggling or if there is a local power cutEnsure the boiler's electrical fused spur switch is fully turned onReset the boiler by turning the selector switch to the 'R' position for 5 seconds
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Why it happens: This fault occurs when the water level inside your central heating system drops below the minimum level required for the boiler to operate safely. The most common reasons for this are a small leak somewhere in your radiator pipework or the air being released from the system through a valve.
Locate the internal filling loop, which is usually a small silver braided hose or a plastic key located underneath the boiler.Open the filling valve slowly to let water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close the valve tightly to stop the flow of water and ensure the boiler resets itself automatically.
Your boiler has stopped working because water is not moving through the heating system quickly enough to prevent the unit from overheating.
Why it happens: This fault occurs when the water inside the boiler heats up too quickly because it is not being pumped away through your radiators effectively. The most common reasons are a failed internal pump, a build-up of sludge blocking the pipework, or air trapped within the heating system preventing smooth circulation.
Check that all radiator valves and any external isolation valves are fully openEnsure your system pressure is at the correct level, usually between 1.0 and 1.5 barBleed all radiators to remove trapped air that might be blocking flow
on the Alpha Pro Tec Plus
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 Alpha 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