E06 displayed, boiler runs but store temperature does not rise correctly or unit locks out

Safety: Isolate electrical supply and allow the system to cool. Be prepared for hot water when loosening pump fittings.

Diagnosis:

• Listen and feel: With power on and a heat demand present, carefully touch the pump body (without removing covers). A working pump will usually vibrate slightly and get warm. If silent and cold, it may not be powered or is seized.
• Check power to pump: Isolate power, remove the pump terminal cover, then restore power and (if competent) measure voltage at the pump terminals when there is a call for heat. If no voltage, suspect PCB or wiring. If voltage is present but pump does not run, the pump is faulty.
• Freeing a stuck rotor: Isolate power and close isolation valves. Remove the pump head and check if the impeller/rotor turns freely with a screwdriver. If jammed with debris or scale, clean and retest. If still stiff, replace the pump head or complete pump.
• Bleed air: Use the pump’s bleed screw (if fitted) or system air vents to remove trapped air that can prevent circulation.

Note: Persistent E06 after pump replacement usually indicates a control or wiring issue that should be investigated by a heating engineer.