If you want to tinker on your boiler you carry on no body will stop you. All trades have there good and bad blokes, I have a good sparks and I charge him a drink to repair his boiler if it goes on the blink, he does the same for me. If you have a rgi in that can't fix your boiler first hit then don't pay I don't go to jobs with a f@ck knows kit of ten parts till I get it right I give the custs a clear cost of part and repair if they are happy I carry on. Anyway what you want will never happen that's fact sorry you feel that your getting the rough end but that's life if you ask a silly question. I'm sure a man of your electrical knowledge can follow your boiler manuel to test the parts you want to test anyway???