Boiler displays A08, no heating or hot water, fan may run but burner does not ignite

Safety: Do not bridge or bypass any safety devices. Identify and correct the root cause.

• Check system pressure and flow: Low water pressure or closed valves can prevent the flow switch from closing. Ensure all isolation valves on the Hoval boiler flow and return are open and system pressure is adequate.
• Inspect flow switch: On models with a mechanical flow switch, check for stuck paddle or debris. Gently tap the housing to free a stuck switch, but if it sticks again, it must be cleaned or replaced.
• Safety thermostat chain: Trace the safety thermostat wiring (overheat, flue stat if fitted) for loose connectors or damaged cables.
• If A08 persists, a technician should test continuity through the safety chain and verify the control PCB input.