High
E66 on Main Combi 30 HE

Your boiler is struggling to direct heat correctly between your radiators and your hot water taps, likely due to a stuck internal component or a sensor reading error.

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

3-Way Valve Assy, Safety Thermostat, or Pressure Gauge

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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