I have searched all over to find some answers, but cant seem to find much. I have an aftermarket tach that I want to hook up to my motor. its a 1985 thunderbird motor, with a brand new RFW wiring harness. I have the tach green wire hooked up to the tach output from the wiring harness, obviously, but the tach still doesnt register correctly over about 2500 RPM. I have also tried putting a pull up resistor (i think 10k) between +12v and the green wire, still same thing. even tried switching the tach cylinder setting between 4, 6, and 8 cylinder, same thing. Is there something im missing? is my tach just garbage?