ON FLASH ON High
Your boiler has detected a problem with its internal temperature sensor and has stopped working as a safety precaution.
Technical description: Thermistor error
Typical repair cost: £100-£180 (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 FLASH ON — no call-out fees, no surprises.
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Parts commonly replaced
- NTC Thermistor
- Wiring harness
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