Help - 24CDi intermittent air pressure fault - diagnosis ?

[Trev37]

Worcester Bosch 24CDi with intermittent failure on HW and CH - following demand everything fires up as normal but sometimes (usually when I'm not looking !) after about 30 seconds fan stops and flame goes out . HW demand lamp flashes fast for 3-4 mins and then goes out. May fire up ok next time or do it again. Fault flowchart J shows this as "Pressure switch has opened .. check flue for blockage and investigate sense tubes and pressure switch". I have had a quick look and Flue & Tubes all seem fine - so I'm guessing problem with fan or the switch. Will take fan off at weekend for a good look but it spins smoothly by hand - no roughness but from outside I think it it is a little noisier than it used to be. Any easy way to confirm the culprit ? I dont want to blow into pressure switch in case I damage it but presume no such issues with cleaning fan end.

Thanks for reading

Trevor

 

[ChrisR]

Will take fan off at weekend

DON'T.
Call a GSR boiler mender.
I can think of several things you need to check that you'd never guess..

 

[OLLIE20]

IF you was gas ragistered, which i assuume you are not, and you was getting an air flow fault of an intermittent nature on one of these, i would check and clean fan under running tap make sure all clear, also do the same with the venturi, as any dirt in these will cause incorrect pressure onto the APS (a little oil into the fan barings wouldnt do any harm) which will then drop out and knock off your burner, you need an RGI to do this as Chris R says

 

[bengasman]