604 High
Your boiler's fan is spinning too slowly to safely clear waste gases, which has caused the system to shut down for safety.
Technical description: CLAS HE RE-Combi EvoE-System EVOClas HE evo CombiClas HE evo System
Typical repair cost: £180-350 (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 604 — no call-out fees, no surprises.
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Parts commonly replaced
- Fan Assembly
- Main Control Board (PCB)
- Venturi Tube
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