Hi you experts, I have a 15 year old camray 3 boiler with a new reillo 40 burner unit fitted recenty as the old one was knackered on too many counts. About one time in 3 the burner does not start up and run cleanly for its 12 secs to light up, but makes several noises as if the electrical power is not getting through to the motor when it first starts up. The same thing happened with the old burner (not why it was changed), so I am assuming it is not the fault of my new burner. IN all other respects the system runs fine lights up OK and runs very smoothly and quietly. Could it be that the control stat is getting old and is not switching over cleanly? I have a new one I got as a precaution a year ago when this problem started- is it time to fit this to cure the fault, is it a difficult job please, or might it be something else?