The "gas vale guys" just guess - just as I guess - they probably guess with more confidence and experience than I do though.
I had the same fault on my Potterton Profile just before Christmas - it was a weak pilot flame not getting the sensor hot enough to let the control board sense it was alight and open the main gas valve for ignition.
Might also be a fault in the control PCB who can say?
A gas valve will cost you close to £200 - A new PCB close to £130 and a pilot injector about £35.
When you call an engineer ask him to diagnose and repair the problem - ask him not to guess at what it may be - could cost you quite a lot if he does and they often guess the most expensive thing first - funny that...
Good luck...
Peccavi, March 2009
