BoilerFaultCodesYour indoor and outdoor units are failing to speak to each other, meaning your central heating and hot water have stopped working.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No connection Outdoor PCB to Indoor PCB (H0)
What causes this fault?
This fault occurs when the digital handshake between your indoor unit and the outdoor heat pump is broken, preventing them from sharing vital operating data. The most common reasons are a loose or damaged communication cable between the two units, or a component failure on one of the electronic circuit boards. Without this constant flow of information, the system shuts down as a safety precaution to avoid running blindly.
This fault can sometimes be triggered during periods of heavy rain or high humidity if moisture enters the outdoor terminal box and interferes with the sensitive data connections.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like 9.1.13 — 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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