Iv got a customer with a vaillant turbo max,black front green control buttons,gc 4704425.wen heating is on,they run hot tap but sometimes goes into lockout,it happens more wen heating has been on for longer periods.iv changed NTC,differential switch,divertor valve opening as it should,Iv even turned the pump over-run down on pcb???.oh changed pump as well any ideas?????

Martin, March 2013

Tried that mate,vaillant don't know answer lol...normally don't get that many problems with these????

Martin, March 2013

Only thing it might be that air pressure switch in not holding just blow the plastic tube if only dirt in it

ltd, March 2013