worcester 350 fails to ignite for hot water

[stucky]

hi there got same problem as brian101 check it out.cheers

 

[superdupergasman]

a link to his post might be nice??

or better still just describe your problem!

 

[stucky]

, Post Subject: Worcester 350 combi fails to ignite



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I've got a problem on a worcester 350 combi boiler that fails to ignite for 10-20 attempts. There is just a flicker of a flame and then it dies. Eventually it fires up and then everything is fine until the system is cold again.

The process of the failing attempts goes like this:-
1) Gas valve solenoid operates
2) Regular spark every half second or so.
3) Very small flame lasts for up to a second
4) Flame goes out
5) Very rapid sparking and what sounds like a relay and the gas valve solenoid rapidly operating.
6) Go through this process enough times and eventually the boiler works normally until it's cold again.

I did find that tapping the relays when going through this process seemed to have a benefitial effect, so I replaced the sequencing board with one I got off ebay, thinking that one of the relays was sticking - no joy

I have pre-heated the flame sensor when the boiler is cold to see if that had any effect - no joy.

Any ideas gratefully received

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[ollski]

temperature sensor usually.

 

[stucky]

hi ollski ive checked temp sensor its fine.problem only when demand for hot water.but the hot water demand is fine when heating is on. ive also replaced flow switchi. i have to keep turning tap on and off until it eventually lights

 

[ollski]

What you've replaced the hot water sensor?

 

[stucky]

it was changed a few years ago .i disconected it and tried the water it wouldnt go hot,connected on again and after a few on and offs it lights up