Don't pay 55 bucks for something thats easy as pie to do yourself...I installed an aftermarket tach and it was really easy. The signal wire for a zetec tour is in a green wire harness that is behind the drivers side fuse box. You will see it if you look(just push the little black knob on the fuse box to open it if it gets in the way) The wire is white with a small black stripe. Its the smallest wire in the whole harness. And all the other wires I just connected them to my other fuses. The wire that is used to light up the tachometer at night, i just attached to my headlight fuse so i can turn it on when my headlights go on. My constant power source wire was put with my radio fuse since my radio has memory and needs constant power. I hope this helped. And of corse you can probably tell where the ground wire goes.
