Having replaced the Thermocouple already it sounds like it must be the Gas Value, but I think that this is beyond my basic skills. I'd like to confirm that it's not the thermocouple before I call for an engineer.
As the subject says I am experiencing a problem with my boiler :( .
When starting from cold the boiler operates for a few minutes then cuts out. After a few restarts it then stays on and work ok. In the process of identifying the fault the system has been drained (X400 and X100) used, the...