BoilerFaultCodesYour heat pump’s main engine has encountered a problem and has stopped running to protect the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Compressor Error
What causes this fault?
This fault occurs when the heat pump's compressor, which is responsible for moving heat into your home, fails to start or shuts down unexpectedly. It is typically caused by a communication failure between the internal electronics or an electrical fault within the compressor unit itself. When this happens, the system stops running to prevent further electrical damage to the expensive internal components.
This fault is more frequent during extreme cold snaps when the compressor has to work at its maximum capacity for extended periods.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like J5E — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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