BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because it failed to light properly or the waste water pipe is blocked.
Why it happens: This fault occurs when the boiler tries to light but cannot detect a stable flame, prompting the system to shut down for safety. The most common reasons are a lack of gas supply, a dirty sensing probe that can't 'see' the flame, or a blockage in the waste water pipe that causes water to back up into the heat exchanger. In many cases, it is simply a sign that the components responsible for the spark or flame monitoring have worn out.
Check that your gas pre-pay meter hasn't run out of credit.Inspect the white plastic pipe (condensate pipe) outside to see if it is frozen or blocked.Attempt to reset the boiler by turning the control knob to 'R' for five seconds.
Your boiler has shut down because its internal safety sensors detected that it was beginning to overheat.
Why it happens: This fault occurs when water inside the boiler reaches an unsafe temperature, triggering a safety switch to prevent damage. The most common reasons are a failed pump that isn't circulating water properly, or a buildup of sludge and limescale that blocks the heat exchanger. It can also be caused by a simple sensor failure where the boiler incorrectly thinks it is overheating.
Ensure all radiator valves are fully open to allow water to circulateCheck that the boiler pressure is between 1.0 and 1.5 bar on the gaugeAllow the boiler to cool down, then turn the selector switch to 'R' for five seconds to reset
Your boiler has stopped working because either there isn't enough water pressure in the system or the internal pump is unable to circulate water.
Why it happens: This fault occurs when the boiler detects that there is not enough water pressure or flow to safely operate the internal heat exchanger. The most common reasons are a simple drop in system pressure that needs topping up, or a mechanical failure of the internal pump which prevents water from moving around your radiators.
Check the pressure gauge on the front of the boiler; if it is below 1 bar, it needs topping up.Locate the filling loop (usually a silver flexible hose) underneath the boiler.Slowly open the valves until the pressure reaches 1.5 bar, then close them tightly.Reset the boiler to see if the fault clears.
Your boiler has switched itself off because it has reached a temperature that is too high, often caused by a circulation problem or a blockage.
Why it happens: This fault occurs when the water inside the boiler gets too hot, triggering a safety switch to prevent damage. The most common reasons are a pump failure that stops water from moving or a buildup of debris like sludge that blocks the heat exchanger. It can also happen if there is trapped air in the system preventing proper circulation.
Check that your radiator valves are open and not turned to zero.Verify that the system pressure is between 1 and 1.5 bar on the pressure gauge.Allow the boiler to cool down, then press the reset button or turn the selector switch to the 'R' position for at least 5 seconds.
Your boiler has detected a problem with its internal temperature sensors, meaning it cannot accurately measure how hot the water is and has shut down as a safety precaution.
Why it happens: This fault occurs when the boiler's control board loses communication with the temperature sensor or receives an unrealistic reading. The most common reason is that the internal thermistor has physically degraded over time or developed a short circuit, preventing the unit from monitoring heat levels safely. In some cases, it can also be caused by loose or damaged wiring connecting the sensor to the main circuit board.
Full guide for 24Your boiler has detected that a temperature sensor is not working correctly, which has caused the system to stop running to prevent overheating.
Why it happens: This fault occurs when the boiler's control board can no longer read accurate information from the flow temperature sensor. The most common reason is that the internal thermistor has physically failed or developed a short circuit, meaning the boiler can no longer safely monitor how hot the water is getting. In some cases, it may also be caused by loose or damaged wiring connecting the sensor to the main control unit.
Full guide for 25on the Potterton Performa System 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 Potterton 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