If that wire doesn't work you could try taking the instrument cluster out. Behind the cluster should be three (if I can remember) plug things that the cluster plugs into (not sure if it's the same for all clusters, this is how it was for my level 2). On the left hand plug the top right wire is the tacho signal wire. Try connect your tacho signal input wire to that and see if it works. I can post pics if I can find my digital camera...