High Lockout
E9 on Ideal HP290

Your heat pump has stopped working because a sensor that monitors the temperature of the cooling liquid returning to the main unit has developed a fault.

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

Compressor Refrigerant Return Thermistor (Th) Error (E9)

What causes this fault?

This fault occurs when the system's brain loses track of the temperature of the refrigerant liquid as it flows back into the compressor. The most common reason is a failed electrical sensor that has either burnt out or is sending back scrambled readings that don't make sense. It can also be caused by a loose connection or a damaged wire between that sensor and the main control board.

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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Related fault codes

E8View →

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