BoilerFaultCodes.com
C7 High Lockout

Your boiler’s internal electronic brain is having trouble communicating with the compressor pump, meaning your heating and hot water have stopped working.

Call an engineer soon

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

Technical description: Inverter Error

What causes this fault?

This fault occurs when the main control board loses its connection with the inverter drive that powers the compressor. It is usually caused by an electrical failure within the inverter’s circuitry or a loose connection in the wiring harness that carries signals between the components. Without this communication, the system cannot safely regulate the speed of the motor, so it shuts down to prevent damage.

This fault can be more frequent during summer heatwaves or extreme winter cold, as the inverter components are sensitive to temperature extremes while working under high demand.

Typical repair cost £450-£900 (including labour)

Engineer required

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

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