High
LED 6 yellow (0) [CH mode] on Ferroli Optima 201

Your boiler has detected a faulty temperature reading caused by a sensor issue, which is preventing your central heating from turning on.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

C.H. sensor (34) short circuit or resistance lower than 500 ohm

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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