I have read a few forums that say this problem is almost deffinately the diverter valve, however my plumber has said that the pin is moving and the micro switch is being activated when the tap is turned, but still ne hot water.

He has spoken to Ariston but they have recommended the secondary heat exchanger or the thermostat or even the board!!!!

Would it be worth changing the diaphams anyway as they are probably the cheaper option??

Paul Ashcroft, June 2010