Boiler shows E08, burner stops, pump may continue to run, temperature rises quickly on display.

Safety first: Allow the boiler to cool before touching the pump or pipework. Isolate electrical power before removing pump covers.

User checks:

• Check system pressure and top up if below 1.0 bar.
• Bleed radiators to remove trapped air, then recheck pressure.
• Ensure all isolation valves under the boiler and on the system are open.
• Reset the boiler and listen for the circulation pump running; a humming noise without flow may indicate a seized rotor.

Technician checks:

• Remove the pump front plug (if fitted) and manually turn the rotor with a screwdriver to free it.
• Check for power at the pump terminals when there is a heat demand; if power is present but the pump does not run, replace the pump cartridge or complete pump.
• Inspect and clean the system filter / dirt separator and flush the heating circuit if heavily contaminated.
• Verify correct operation of any external zone valves.

Persistent E08 faults require professional diagnosis to prevent damage to the heat exchanger.