BoilerFaultCodesTechnical description
Flame detector input signal is outside the limits (0 or 5 V) | Electronics defective
What causes this fault?
This fault occurs when the boiler's main control board receives a corrupt electrical signal from the flame sensing system, making it unable to verify if the burner is safely lit. The most common reason is a communication failure within the internal circuitry, often caused by a short circuit or a component failure on the printed circuit board itself.
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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