Smith Tachometer Signal Hook Up - Need Solution

[GWL]

I've got original Smith Gauges from Nisonger. I talked to them and they said the signal it needs is a pulse. Ford Performance says their signal is a square wave.

So my tachometer does not work.

Ford Racing/Performance wiring harness. This harness has a Control Module next to the standard EEC-IV computer. A tan wire, for the tachometer, comes from that Control Module and runs to my tachometer but, as I said, the tachometer doesn't work.

Ford Performance suggested a Tach Adapter. Has anyone used one of these and what adapter would you use? These darn things run over $60 and I guess change the signal so the tachometer can read it.

Thanks, George

[GWL]

I've been doing some research.

Found the Smith gauges web site in the UK. Their tachometer reads a square wave signal or pulses. I guess they are the same thing. The pulses come closer together as the engine speeds up and is read by the tachometer.

So, maybe my new tach is broken? I can run a wire from the coil to another unused tach wire for that purpose and see if that works.

Any other suggestions?

Thanks, George