BoilerFaultCodesTechnical description
Temperature measured by return sensor greater than flow sensor.
What causes this fault?
This fault occurs when the boiler detects that the water returning from your radiators is hotter than the water it just sent out, which contradicts the laws of physics in a normal system. The most common reasons are a pump that has failed or is struggling to push water around, a blockage in the heat exchanger, or temperature sensors that have become uncalibrated and are giving false readings.
This issue often surfaces in autumn when the heating is turned on for the first time after summer, as internal pump components can seize during long periods of inactivity.
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.