sorry no diagramme or pic so i will describe,inside of my vokera 28 he boiler top right hand side i have a small square black plastic box with some wires comeing of it is this a ignition regulator or something else i have been told that this is the fault and needs replacing i have no heat or hotwater and the boiler is just over 3yrs old,how much to replace and how much to purchase ,could i do it myself any help please thanks