Baxi 105e Flame Failure Problem

[mickyq]

bronzino i took the boiler cover off to change the pressure switch. im not gas safe registered. have I done something illeagal or unsafe?

 

[GQuigley67]

you shouldnt be working on boilers if your not competent to do so i.e GSR, if you are competent and not GSR you can work on your own boiler but not anyone elses

 

[dles1966]

Final update - I've now run the CH on 3 seperate occassions for a total of 9hrs without a problem, same time as using DHW.
Conclusion
Water in the gas main external to my property caused some contamination of the gas valve filter. This in turn caused a reduction in flow/pressure supplied to the gas valve which led to a drop in supply pressure of 1mb. Whilst not a problem to the maximum pressure it was a problem to the minimum required pressure of 2.5mb, pressure actually measured at 1.5mb. I estimate that 4% loss of flow through the gas valve filter would lead to a 1mb drop in pressure.
Suggestion
Baxi should make the filter a servicable, replacable part so it can be checked and/or replaced during annual service.
Baxi should enhance their troubleshooting guide to indicate checking min pressure when any flame/burner issues are being considered.

Thanks again to all who helped me think this issue through.

Hi quietman, I have a very similar problem, however did you happen to notice if the "burner on" neon lit when you had the fault? as mine does not yet it does light then flame goes out after 9 seconds?

I suspect low flow/pressure, but might be caused by the filter being blocked or at least filthy. Or I also suspect the modulator.

I will need to try the same as you with the "U" tube connected.