Vokera HE Compact- Only fires when the front cover is off

Is there an obstruction inside the flue where the sensing tubes enter the airstream? This could be down to corrosion within the venturi. Alternatively leaves or cobwebs obscuring the air inlet or flue outlet. (Other causes not discounted)

================================== A remote possibility...

My boiler gave the same symptoms for a quite simple fault. The boiler would only fire up with front cover removed and it did this consistently. Every time the cover was replaced it failed to fire up. When I removed the cover to try again I noticed that the small ignition lead was sparking against the boiler chassis and no spark was reaching the correct ignition point. The ignition lead was being partly trapped when the cover was replaced. The strange thing is that the insulation on the ignition lead appeared to have broken down spontaneously - no physical damage visible. In my case the lead was able to spark normally until it was pushed against the chassis, so you might try moving your ignition lead about to see if it does the same.

Cic.

replying to ARWadworth, Sukhdev wrote: clean the venturi on the fan.

I don't think he wants to know now - 9 years after he posted the question.

Hint: the web portal you are using likes to promote questions from a decade ago as a current topic.

Yes its a bloody mess and they have been told what a heap of crap their interface is. I'm not totally sure if they even care. After all they pass this place off as theirs, when it is clearly a Usenet group and these have been around for longer than the web has. If anyone wants to use it legitimately first try to figure out if the post is very old if possible then quote part of it in your reply, at least that way people here will know what its about. Nobody is going to go on that web site to fiddle with the interface to do what they can do perfectly well with software meant for the job of using the newsgroups. Brian

This might assist you with posting to a newsgroup, albeit through a website:

- If you are sending a reply to a message or a posting be sure you summarize the original at the top of the message, or include just enough text of the original to give a context.

replying to ARWadworth, Anthony Savill wrote: Hi did you find the problem with your boiler as i have the same problem thanks

Check the date of the post you to which you are replying. It's 10 years ago!