BoilerFaultCodesThe 6 most common faults
Your boiler is failing to ignite and has locked itself out for safety after several unsuccessful attempts to start.
Why it happens: This fault occurs when the boiler tries to light the flame several times but fails to detect a successful ignition. It is usually caused by a worn-out ignition component that can no longer create a spark, or an issue with the gas supply preventing fuel from reaching the burner.
Check if your gas supply is turned on at the meterIf you have a prepaid gas meter, ensure it has creditPress the reset button once to see if the boiler restarts
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Why it happens: This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety sensor to cut the power. The most common reasons are a failed internal pump that isn't moving the water away fast enough, or a build-up of sludge and debris blocking the flow of water through the system.
Check that all radiator valves are fully open to allow water to circulate.Ensure there is no air trapped in the system by bleeding your radiators.Press the reset button on the front of the boiler once it has cooled down.
Your boiler has detected that the water leaving the unit is getting too hot, causing it to shut down to prevent damage.
Why it happens: This fault occurs when the water inside the boiler heats up too quickly or exceeds a safe temperature limit. The most common reasons are a pump failure that stops water from moving through the system, or a buildup of limescale and sludge that restricts flow within the heat exchanger.
Check that all radiator valves are fully openCheck that the external pump (if visible) is running and not stuckWait 20 minutes for the unit to cool down and try resetting the boiler
Your boiler is not receiving any electrical power, which is why the lights are off and it isn't working.
Why it happens: This fault occurs when the boiler's control system detects a complete break in the electrical circuit required to run the unit. The most common reason is a blown fuse or a loose connection in the wiring, which prevents electricity from reaching the internal components. In some cases, a surge may have damaged the main circuit board, causing it to fail entirely.
Check if your home's main consumer unit (fuse box) has tripped.Ensure the boiler's isolation switch (usually a white switch near the boiler) is turned on.Check the fuse in the boiler's fused spur switch, replacing it with a 3-amp fuse if necessary.
Your boiler has become too hot and has automatically switched itself off to prevent any damage.
Why it happens: This fault occurs when the water inside the boiler reaches a dangerously high temperature, causing a safety switch to cut the power. The most common reasons are a pump failure that stops water from moving around the system or a build-up of sludge that blocks the heat exchanger. In some cases, the thermostat itself may have simply worn out and is giving a false reading.
Check that all radiator valves are open to allow water to flowAllow the boiler to cool down completelyPress the reset button (D) located on the control panel
Your boiler has detected that there is not enough water in the central heating system to operate safely, so it has shut down to protect itself.
Why it happens: This fault occurs when the water levels inside your radiators and pipework drop below a functional level, meaning the boiler can no longer circulate heat safely. The most common reason is a tiny leak somewhere in the system or because the air was recently bled out of your radiators without topping the water back up. In some cases, a failing internal component like the expansion vessel may be causing the pressure to fluctuate and escape.
Locate the filling loop, which is usually a flexible silver hose with two small valves underneath the boiler.Slowly open both valve handles until you hear water entering the system.Watch the pressure gauge and close both valves tightly once the needle reaches 1.5 bar.
on the Ideal Classic FF
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