i bought my manual used with no tach in it but im putting an aftermarket one in now... unfortuntely, ford didnt have the wires all together so i could just plug it in when you take out the instrument cluster. so i went down to the dealership and looked in some books and found out where the wires for the ground, power and illumination go and plugged them in. what i havent found out or done is the 4th wire that has to hook up to the ignition coil. in my 4.2 there are 4 wires in a connector that plug into the coil. i was wondering if any of you guys have done this and know which wire to hook the tach up to for a reading. its in a really bad position and i dont want to do the trial and error thing.

thanks

 

The 4th wire needs to be sodered into the wiring harness on the pcm... should be #48 pin... you might be lucky and there is a red/white wire coming out.. and then you tap into that wire...