It all depends. The basic tack is different. The XR7 tachs internals are the same as the Mustang but the cases are not identical, but you can make it work with a little creativity. The warning lights are different too.

You can get it rebuilt/repaired by Tachman, or get it converted to a modern Tach by Rocketman

Tachometer Repair Restoration for Antique Classic Cars Auto

Rocketman Tach

 

Please clarify the difference between a vintage and modern tach. The 68 has electronic ignition, so that already requires a converter. Would either way work, or otherwise what are the pro's/cons or a rebuild vs modern?
Thanks

 

In a vintage Ford power comes from the ignition switch and goes to the coil through a resistance wire. (The wire lowers the voltage). When installing a vintage tach, it goes between the ignition switch and resistance wire. Every time the coil fires it creates a pulse in the wire. The tach translate these pulse into an engine RPM. This is very accurate way to measure it. The downside is that if the tach fails it can prevent the flow of power to the coil and the engine won’t run.

Modern three wire tachs tap the ignition power prior to the resister wire and have their own ground. They also use a signal wire to provide pulses. In this way they are isolated from the ignition system’s pr8mary wiring. This syste is a little less accurate, but more reliable as failure won’t prevent the ignition system from working. Depending on your ignition system the signal wire can come from different places. See the following diagram from Rocketman’s website on proper connection options.

 

Sending it to Rocketman will eliminate the need for the converter. He will put modern guts in it. Then you don’t have to worry about that transformer anymore. Or what type of ignition you decide to use now or in the future.

 

And if you go with the modern three wire setup, the engine will still run if the tach ever goes south again, because it will not be wired inline as a series circuit like the factory original two wire tach was. And last time I checked, even Tachman repairs them as three wire setups as the old D'Arsenault (forgive my lame spelling..) factory style movements are pretty much all gone/used up by now.

 

Cougar tachs have a different face printing than Mustangs do.

Look up Phil Severence in Idaho for repairs. a $75 original tach? Maybe 40 years ago.....

 

Can you show us the face of the Cougar tach so we can identify it. If it is in good shape a qualified repair shop like Tachman can use the internals to fix your original Tach. Otherwise you are looking at converting it to three wire.

 

I don't have a picture of the Cougar tach, but now realize they have differences including the face so it appears the best option is to have my tach rebuilt. Thanks for the help.

 

Here's a cougar dash, 67
https://www.hemmings.com/blog/2016/...om/blog/2016/09/30/year-make-and-model-1967-68-mercury-cougar-xr7/#&gid=1&pid=4

https://www.google.com/search?q=67+...ved=2ahUKEwj5pYXZl7fiAhWEdd8KHRekDR4Q9QEwCnoECAYQGA#imgrc=3D54FBC1SSb8uM:&vet=1