ON OFF FLASH High
Your boiler has detected that the electrical wiring coming into the unit is connected the wrong way around, causing it to shut down for safety.
Technical description: Live and neutral reversed error
Typical repair cost: £80-160 (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 ON OFF FLASH — no call-out fees, no surprises.
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Parts commonly replaced
- External wiring connections
- Printed Circuit Board (PCB)
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