B

▶ Check the flow through the appliance and that the system is filled.
▶ Check for air locks in the system and purge if required.
▶ Check the isolation valves, ensure they are open.
▶ Check the pump is operating freely and check the voltage to the pump.
▶ Check the heat exchanger sensor and the flow sensor are making contact with the pipework.
▶ Check the heat exchanger sensor and the resistance of the temperature sensor and replace if required.
▶ Check the continuity of harness and replace if required.