Rev counter wiring

[pionte]

I am just about to fit an aftermarket rev counter to my 1.9 DG , It is only 3 wires, positive, negative and negative to the coil neg, My question is , is there already wiring installed to connect too? My van never had one fitted from the factory but if a standard wiring loom already has this neg wire then it would be far easier to pick up the feed rather than run a wire all the way back to the engine bay.

[kevtherev]

black wire to earth
red wire to positive switched power
green wire to negative side of coil that goes to points
white wire for back light, so tap into speedo light or similar