Britony combi se

[MBPlumb]

Hello wondering if anyone can point me in the right direction. I went to look at this combi earlier and it is giving me flame detection fault. the ignition process starts fan and pump run, but then stops before even attempting to ignite. The air pressure switch seems to be working ok the ,continuity is switching between connections. The fault find is rubbish in the manual, its telling me pcb but im not sure i though I thought it would gas valve next in series? Technical help is closed for the bank holidays anyone able to offer some advice in the mean time?

Thanks Ben.

[gas man]

have you checked, ventures,tubing,ignition cartridge/spark generator?

[tipintim]

Does solinoid on gas valve click.

[MBPlumb]

the tubing seemed intact, im no longer with the boiler so cant check on anything right now. The fan seems to run to approx 2-3 secs before cutting out. If it were the spark generator i would imagine it would run for longer as im guessing it wouldnt recognise the fault that soon. There is no click on the gas valve, if it were the gas valve would it cut the fan out that quick or would the ignition process continue a bit longer?