BoilerFaultCodesThe 6 most common faults
Your boiler has switched itself off because it got too hot, and it needs to cool down before it can be restarted.
Why it happens: This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety switch to shut everything down. The most common reasons are a failed pump that isn't moving water away from the boiler quickly enough or a blockage in the system pipework. It can also happen if the main control thermostat fails and allows the burner to stay on for too long.
Wait at least 15-20 minutes for the boiler to cool down naturally.Locate the manual reset button (marked E) on the control panel.Press the button firmly and attempt to relight the pilot light following the instructions on the boiler's flap.
Your heating system is losing water, which means there is likely a leak or a failing pressure relief valve causing the boiler to stop working correctly.
Why it happens: This fault occurs when the sealed system no longer has enough water to circulate heat safely, triggered by a physical escape of water from the pipework or components. The most common reasons are a weeping connection on a radiator valve or a internal part like the expansion vessel failing, which forces water out through the safety discharge pipe.
Check all visible radiator valves and pipework for signs of wet patches or stains.Locate the filling loop (a silver flexible hose) and carefully top up the pressure until the gauge needle matches the red marker.Run the heating and re-check for leaks if the pressure drops again immediately.
Your boiler is unable to start the small flame needed to ignite the main burner, meaning your heating and hot water will not work.
Why it happens: This fault occurs when the boiler's small pilot flame fails to stay lit, which is necessary to safely ignite the main heating burners. The most common reasons are a buildup of soot blocking the tiny gas nozzle or a worn-out sensor that can no longer detect the heat from the flame.
Full guide for 49Your boiler's pilot light is going out as soon as you let go of the ignition button, preventing the main burner from starting up.
Why it happens: This fault occurs when the boiler's safety system fails to detect a steady pilot flame, causing it to shut off the gas supply for safety. The most common reason is a worn-out thermocouple that can no longer generate the small electrical current needed to hold the gas valve open, or a build-up of soot blocking the pilot assembly.
Full guide for 50Your boiler has successfully lit the small pilot flame, but the main burner is failing to ignite to provide heat or hot water.
Why it happens: This fault occurs when the boiler's internal safety sensors detect that the initial pilot light is burning correctly, but the instruction to open the main gas supply is failing. The most common reason is a mechanical failure within the gas control valve or a faulty solenoid coil that is unable to physically pull open the valve to let gas reach the main burners.
Full guide for 51Your boiler has managed to light the small pilot flame, but the main gas burners are failing to ignite to heat your home.
Why it happens: This fault occurs when the boiler successfully lights the small starter flame but cannot open the main gas valve to fire up the large burners. The most common reason is a mechanical failure within the internal gas control valve or an electrical fault in the circuit board that prevents it from sending the signal to release the main flow of gas.
Full guide for 52on the Ideal Mexico Super CF3 40-80
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 Ideal 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