4 green High

Ferroli 4 green Fault Code

Also written as 4GREEN — same fault.

The Ferroli 4 green fault code means: your boiler's internal temperature sensors are stuck in a mode that is telling the system to stay on, which can lead to overheating or your heating staying on when it shouldn't.. It appears on 1 Ferroli model in our database.

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: Sensor (34) or (42) calling for heat
Typical repair cost £90-160 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Ferroli models that show the 4 green fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Ferroli 4 green fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026