Hi I have a ecotec pro 28 showing f75 fault when system is drained down it is still showing 1.6 bar when u press minus button boiler yet the gauge is at zero!! I have removed water sensor and cleaned all seems ok and I'm getting a good reading across it plus I have removed pump and it is working fine. I have removed where the gauge fits into behind the pump but no blockage there either! I pumped ex vessel to one bar too but it just keeps coming up f75 any ideas folks??