biasi 24s fan?

[stevetheplumber]

looked at a biasi on the way home tonight pump runs fan cuts in but then cuts out imediatleyany one give me an idea where to start if it was a neta heat id say board but im still playing catch up with combis

 

[mikegas]

could be aps, tubes venturi

 

[mfgs]

fan, air pressure switch, pcb. I would start by testing those.

 

[Gascat]

heating circuit flow switch or what they said ^^^^^^^^^^^^