21 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: ecoTEC plus 618
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Your boiler has lost connection with its main internal temperature sensor, meaning it cannot safely tell how hot the water is and has shut down as a precaution.
Your boiler has stopped working because it cannot correctly measure the temperature of the water returning to the unit due to a faulty sensor or connection.
Your boiler has stopped working because a sensor that monitors water temperature has developed an electrical fault.
Your boiler has stopped working because one of its internal temperature sensors has developed an electrical fault and is giving an incorrect reading.
Your boiler has lost connection to the hot water cylinder sensor, meaning it cannot tell how hot your water is or when to heat it.
Your boiler has switched itself off because it has reached an unsafe temperature and needs to cool down before it can restart.
Your boiler has detected that there is not enough water pressure in the system to operate safely.
Your boiler is struggling to circulate water properly, often because the system pressure is too low or there is trapped air preventing the heat from moving away from the boiler.
Your boiler is overheating because water isn't moving through the system quickly enough to take the heat away.
Your boiler has detected that the water pressure has dropped too low or there is a problem with the internal sensor that monitors it, causing the system to shut down for safety.
Your boiler has detected a signal error between its control system and gas supply, preventing it from lighting safely.
Your boiler has failed to ignite, which means it cannot light the gas flame required to provide heat or hot water.
Your boiler has lost its gas supply or the flame has gone out and it cannot restart itself.
Your boiler's fan is struggling to spin at the correct speed, which prevents the unit from starting up safely to heat your home.
Your boiler has detected an electrical fault with the part that controls the gas supply, meaning it cannot ignite safely for heating or hot water.
Your boiler has detected an electrical problem with the system that controls the gas flow, meaning it cannot light safely for heating or hot water.
Your boiler has detected that the gas valve is not closing properly or there is a communication error between the gas valve and the control board.
Your boiler's internal computer brain has developed a memory error and cannot process the instructions needed to run safely.
Your boiler has detected an electrical issue with its internal heat sensors or the main control board, preventing it from heating your home safely.
Your boiler's internal control board has become too hot to operate safely and has shut down to prevent damage.
Your boiler has detected a flame when there shouldn't be one, or has a confusion in its internal electronics, causing it to shut down for safety.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes