C4 237 High
Your boiler's main internal computer has developed a serious electronic fault and can no longer control the heating process safely.
Technical description: Control box or heat control module (HCM) is defective
Typical repair cost: £250-£550 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like C4 237 — no call-out fees, no surprises.
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Parts commonly replaced
- Printed Circuit Board (PCB)
- Heat Control Module (HCM)
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