BoilerFaultCodesTechnical description
Return/flow sensor fault from possible failure of one or both sensors
What causes this fault?
This fault occurs when the boiler's control board detects that the temperature sensors (NTC thermistors) are sending conflicting information or no signal at all. The most common reason is a physical failure of the internal sensor probes, but it can also be caused by loose wiring or mineral buildup on the sensors preventing them from reading heat levels accurately.
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.
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