my myson,which is 21yrs old is making a loud banging noise when it is fully hot.i have changed the 3way valve and pump.when it banged again i checked the pump and found that it was not running,although there was 240v to it.the room stat,cylinder stat were made,also the boiler was running.i suspect i am not getting a signal from the boiler.if so, could this be a boiler stat problem.