Between them, they have replaced the following parts in the boiler :-
- Extractor fan assembly, (wouldnt been my first choice)
- Wax capsule, (see above)
- Thermocouple,(hmmm possibly but wouldnt of thought so)
- auto air vent, (reasonable choice, air in exchanger)
- flowswitch assembly,(nope)
- microswitch, (see above)
- overheat stat.(very possibly)
To me without checking it does seem like a heat problem and pretty sure o/h stat is interrupter to thermocouple so if triggered, gas off. Triggered cos a faulty stat or due to a failing exchanger (as twin pass) would be my first thoughts but like i say, it would be a good look over first confirming pressures etc.
ste
December 2009