Worcester Bosch d1 Fault Code

What causes the Worcester Bosch d1 fault?

This fault occurs when the internal sensor responsible for measuring the temperature of the water coming back into the boiler has malfunctioned or lost its connection. This is usually caused by the sensor's internal components wearing out over time or from moisture damaging the electrical pins on the wiring harness. When the boiler cannot accurately measure this temperature, it shuts down to prevent the system from overheating.