Your boiler has detected a fault with its internal temperature sensor, preventing it from heating your water and radiators safely.

primary NTC open/short circuit

What causes this fault?

This fault occurs when the boiler's main temperature sensor, which monitors the heat of the water inside the unit, fails or loses connection. The most common reason is that the internal component has simply worn out over time or a wire has come loose, meaning the boiler can no longer safely regulate its own temperature.