BoilerFaultCodesYour boiler's main internal computer or memory chip has developed a communication fault or has failed, meaning the unit cannot safely control the heating process.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Control box or heat control module (HCM) is defective or loose, the HCM needs to be checked
What causes this fault?
This fault occurs when the boiler's central brain loses contact with its memory chip, which stores the specific settings required for your model to operate. It is usually caused by a loose connection where the chip plugs into the circuit board, or the internal electronic components have simply worn out and failed over time.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 9U233 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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