Potterton 40 boiler

[clanharty]

I have a Potterton 40 boiler. Has been working fine for past 5 years and regularly serviced. Now has odd fault - when timer for CH and HW come on the boiler tries to fire up, fan comes on but after 10 secs will stop. A few secs later it will try again but switch off after just 2 or 3 secs. Took access covers off and could hear Air Pressure Switch clicking on and then off. A friend suggested blowing warm air up into the APS with a hairdryer - tried this and the system immediately switched on and is currently running all OK.
Is it the APS which needs replacing or is it more complex than that e.g. read on another thread it may be blockage in APS hoses?
Any ideas welcomed before I buy a replacement APS and find it is not the fault! Thanks.

 

[Agile]

We really need to know what boiler model you have.

It sounds as if you had moisture in the tubes to the APS.

I suggest you look at the flue which should slope DOWNWARDS towards the outside.

Also see if there are over flowing or broken gutters above the flue?

We have had some very violent weather conditions recently so it might be just a one off occurance.

I dont think you should be changing the APS.

Tony

 

[clanharty]

Thanks for post, Tony.
Have more details on boiler - its a Potterton FF 40 boiler GC No. 41 719 06.
Have checked flue/gutters etc and no obvious condensation and/or water ingress.
Anything else I should look for or be testing on the system? Wife has told me not to turn off the system until I KNOW I can get it back on again!!

 

[clanharty]

Hi again!
Switched system off and tried starting from timer as would be usual. Same thing as before - tries starting up, APS clicking but system cuts out after 2 - 3 seconds. Used hairdryer underneath the APS and "whoomf" it all starts up normally.
Have looked down flue etc and can't see any condensation. Any ideas as to what it could be? APS seems the likely culprit but any other ideas welcomed!

 

[twgas]

PCB is normally cause of fan starting/stopping/starting/stopping/....

 

[clanharty]

Thanks Mick - will search for new PCB.