BoilerFaultCodesTechnical description
Appliance is within the waiting period of the operation block function due to water shortage (temperature gradient)
What causes this fault?
This fault occurs when the boiler's internal sensors detect a sudden, sharp rise in temperature because water isn't moving through the heat exchanger fast enough to carry the heat away. The most common reasons are an air lock trapped in the pump, a buildup of sludge blocking the pipework, or a failing circulation pump that can no longer push the water around your radiators.
This code is frequently seen in autumn when the heating is turned back on for the first time, as pumps can seize up after sitting idle throughout the summer.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.