Boiler Breakdown Sticky

[ShaunCorbs]

Attended a 24ri a few days ago with just the blue light flashing - would not fire & was working up until yesterday.
Worcester fault sheet suggested:
Gas pressure
Co2 levels
Electrodes
Gas coils
Possibly pcb.
In other words could be anything.
I picked up a set of electrodes & a gasket.
On removal the rectification electrode was a bit short but the electrodes were sparking.
Removed the fan & found part of the rubber flap in the air-gas mixing chamber was missing. The other bit had passed through the fan & was sitting in the bottom of the burner.
Another merchant visit new flap installed & boiler rebuilt.
Still exactly the same fault.
Both coils tested & good resistance 35v being sent by board so all ok there. Gas pressure 23mb but noticeably no drop when the boiler was trying to fire. I would have expected a good 1 or 2 mb drop when trying to fire so deduced that the gas valve had also failed. Fortunately had a spare in the van which does several of the Worcester range.
Factory reset as a start point & apart from 440ppm it fired.
All adjusted to book Co2 settings.
In all about 5 hours including merchant visit.
So the fault sheet was more or less correct in that all those things were wrong with the exception of the pcb.
A bit unusual to get 3 parts fail at once, fortunately the customer was perched on my shoulder & could see each faulty part as they were uncovered.

Regards

Arthur

Love a good brain tease