BoilerFaultCodesThe 6 most common faults
Your boiler has reached an excessively high temperature and has shut down as a safety precaution to prevent damage.
Why it happens: This fault occurs when the water inside the boiler gets too hot, triggering a safety switch to shut the system down. The most common reasons are a pump failure preventing water from moving through the unit, or a internal blockage like air or sludge that is trapping heat in the heat exchanger.
Check that all radiator valves are fully open to allow water to circulate.Ensure your system pressure is between 1.0 and 1.5 bar on the front gauge.Try resetting the boiler by turning the selector knob to the 'R' position for five seconds.
Your boiler has lost water pressure and has stopped working to protect itself from damage.
Why it happens: This fault occurs when the water pressure inside your heating system drops below a safe level, causing the boiler to shut down to prevent overheating. The most common reason is a small leak in the pipework or radiators, though it can also happen if you have recently bled your radiators and haven't topped the water back up.
Locate the filling loop (the flexible braided hose) underneath or near the boiler.Slowly open the tap or valve(s) on the loop while watching the pressure gauge.Close the tap or valve(s) tightly once the gauge reaches between 1 and 1.5 bar.
Your boiler is not receiving enough gas or is struggling to light the flame needed to heat your water and radiators.
Why it happens: This fault occurs when the boiler tries to ignite three times but fails to establish or maintain a steady flame. The most common reasons are an interruption in the gas supply, a blocked pipe, or a component inside the boiler being unable to create the spark needed to light the gas.
Check that your gas emergency control valve is open and any prepaid gas meter has credit.Ensure other gas appliances, like a hob, are working to confirm gas supply to the property.If it is freezing outside, check if your external condensate pipe has frozen and gently thaw it with warm water.Press the Reset button for five seconds to attempt to restart the boiler.
Your boiler's internal temperature sensor has stopped communicating correctly, preventing the system from heating your radiators.
Why it happens: This fault occurs when the boiler's control board loses communication with the temperature sensor responsible for your radiators. This is typically caused by the internal sensor failing due to age or a loose electrical connection in the wiring harness that prevents the boiler from monitoring how hot the water is.
Full guide for E20Your boiler is currently unable to sense the temperature of your hot water, so it has stopped producing it to prevent potential overheating.
Why it happens: This fault occurs when the boiler's internal safety sensors detect that the exhaust gases are too hot or cannot escape the property correctly. It is often triggered by a breakdown in the sensor that monitors flue temperatures, or a physical blockage in the pipe that carries waste water away from the unit. When the system can no longer safely vent heat or clear condensation, it shuts down to prevent internal damage.
Full guide for E28Your boiler's hot water sensor has stopped working, so the system is unable to tell how hot your water is and has stopped heating it for safety.
Why it happens: This fault occurs when the internal sensor responsible for monitoring your hot water temperature fails or sends an incorrect signal to the main control board. The most common reason is that the sensor has physically degraded over time or developed a short circuit, meaning the boiler can no longer safely verify how hot the water is. Occasionally, loose or damaged wiring between the sensor and the boiler’s computer can also trigger this shutdown.
Full guide for E50on the Baxi Platinum Combi HE
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 Baxi 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