Your boiler is struggling to accurately measure the temperature of your hot water, which usually means the water will either be too cold or the system will stop providing hot water altogether.

DHW thermistor error

What causes this fault?

This fault occurs when the internal sensor responsible for tracking your tap water temperature fails or sends an incorrect signal to the control board. The most common reason is that the sensor has physically degraded over time or developed a faulty electrical connection, preventing the boiler from knowing how much to heat the water. To protect you from scalding or damage, the boiler will usually stop heating the water until the part is replaced.