Vokera Compact 29 HE won't ignite without the case cover seal removed....?

[theanalyst]

Had a but of a head scratcher this morning chaps.
Vokera 29kw compact, About 4 years old...
I've been stressing majorly trying to fix it on a callout this morning, eventually put a new APS on it even though the old one seemed fine. NO change.
The boiler fires (mostly) with the case cover off, but just fast flashing green light, fan and no ignition sequence with cover back on.

I was suspecting the fan may be the problem, is there any way to prove this beyond all doubt? I was thinking I should have removed one of the tubes from the fan manifold and see if it worked ok (pressure equalisation problem?)

cheers

I've tested power at the PCB pins as per Vokeras crappy manual and all seems ok!

http://www.ukplumbersforums.co.uk/plumbing-forum/19726-vokera-compact-25-only-works-case-3.html

 

[mfgs]

To get the fan out to clean the venturi, you just need to unscrew the flue hood on top of the burner and slide that out with the fan attached to it. Only need to slide it out about 3-4 inches to be able to get at the venturi. No need for a drain down and no way were you ever going to get at those screws under the fan in the flue hood with it still in place.

 

[theanalyst]

To get the fan out to clean the venturi, you just need to unscrew the flue hood on top of the burner and slide that out with the fan attached to it. Only need to slide it out about 3-4 inches to be able to get at the venturi. No need for a drain down and no way were you ever going to get at those screws under the fan in the flue hood with it still in place.

Im pretty sure we tried every possible combination, probably except this lol
Vokeras instructions about fan removal were very poorly written so cheers for the heads up