Biasi Boiler m90e 28s problem

[presston]

Hi Hope someone can help

My biasi boiler has suddenly started going on and off every 10 seconds or so when the hot water is turned on and also when just the central heating is on.
There are no faults indicated on the flashing led and the pressure is around 1.5 bar. I am an electrician so is there anything i can do to rectify the problem or will i need a corgi engineer
Thanks

 

[presston]

Also when in diagnostic mode it doesnt show any faults. when the hot water is turned on the outer two leds flash alternately and when the c.h. is on the outer two flash at the same time. meanwhile the boiler is still igniting and then going out. if i leave it for awhile igniting and then going out the central heating will eventually stay on. i have cleaned the detection electrode.

 

[presston]

Hello

Found the problem to be down to the air pressure switch. The switch is ok so i presume the problem to be with the venturi. I have noticed that when the boiler first comes on a puff of steam comes out of the flue. Could it be that there is water in the venturi. Is it possible to clean it. I realize i will have to have a combustion check afterwards. If i got the boiler serviced is this part of the service or would this be extra.
Thanks

 

[transam]

Flue or fan .

 

[presston]

The steam is coming out of the flue on the outside of the house

 

[transam]

steam , pluming, products of combustion , exiting flue thats normal !!! U need to get your flue / fan checked by your rgi !!!