Chaffoteaux combi boiler shows flashing green 70/80 intermittently?

I've got the same problem just had the pressure switch replaced but that didnt work its had a few plumbers scratching their heads its been like it 3 months now and the reset button isnt solving the problem anymore none of them have said anything about the probe switch 1 said it was the pcb needed replacing another said it was the ignition gone and the last 1 replaced the air pressure switch just cant work out what the problem is

paul
March 2010