My Altech 010 seized (motor & valve), so I ordered another off eBay. After it arrived, I removed my duff one, and when I opened the new box it was actually a Salus! Not the end of the world I thought, so I swapped over the valves, but now I'm connecting the wiring, there's one white wire left over from my original head. Is this spare, or meant to be used? Thanks in advance forum.