We have a gas central heating system and our problem started last year, when the boiler and pilot light kept cutting out. We had a couple of engineers in, one who changed the wiring saying it was wrong? and another who changed lots of parts including the gas valve and it did get much better. In fact it was working perfectly between December and last week. Last week my husband bled one of the radiators, whether this caused it or whether it was the change to a milder temperature, I have no idea but since then, the boiler cuts out after being on for a couple of hours, sometimes sooner. The boiler and pilot light cut off. It is in fact the gas valve that shuts down and sometime you can't restart it for an hour or so.
I think you should get an engineer in who knows what he is doing as the two you have had so far don't appear to.
If the wiring was wrong from the outset the system shouldn't have worked until last year. By te sounds of it the second one was guessing and just changed parts until it worked! If that sounds cynical I'm afraid it is.
You don't mention the make model etc details on your boiler. One of the boiler guys like htg engineer or Steve the gas may be able to give you a good steer armed with that information.
Hi, not much to go on but if sealed system eg combi, bleeding rads may have lowered system pressure close to boilers cut out pressure.
If boiler has pressure gauge it should be at around 1.5bar with boiler on.
If under 1 bar needs raising with filling loop, unless you are sure how to do that correctly get a professional in as over doing it could damage boiler, also filling loop must be removed after use.