i have a valiant eco plus combi boiler and keep getting a F.75 fault which i have looked up i keep filling up and make sure that the presure on the digital readout is at about 1.5 bar but when heating system comes on when you look at the manometer it s going into the red but if the pressure is at around 1.3 bar it starts to go in to the fault code

azz, December 2008

its a blocked water pressure sensor, the one with the salmon coloured plug attatched with 3 wires white,red,green i think the colours are.

paul, December 2008

expantion vessel may need to be represurised

b, December 2008

f.75 = Water pressure sensor or/and pump defective
too little water in appliance.

a, December 2008