... behind the roof stoplight on my 2016 X250 PVC. I've no idea if it is live. It has the same 3-pin connector as the stop light, which of course isnnot connected to anything. My first thought was reversing light power. I know that often these loose wires result from the use of standard wiring looms, with extras not having been fitted. Any ideas? Are there any other spare wires which can be used?