Your boiler is having trouble measuring the flow of hot water, which could mean your taps don't get as hot as they should or your hot water fluctuates.

What causes this fault?

This fault occurs when the internal sensor responsible for tracking how much water is moving through the system fails to send a clear signal to the main control board. The most common reason is that the sensor's internal components have worn out or become blocked by debris, preventing it from accurately telling the boiler to fire up for hot water.