I found a mercury topaz with a Mazda RF Diesel in it. It seems to have a tachometer that was fed by the Alternator W Terminal... Could anyone confirm or deny this?
About what year is that Topaz, it could make a difference.. I looked up an '84 on Alldata.. Info is vague for the diesel specific stuff, but the wiring diagram shows an "engine speed sensor".. One terminal of the sensor is grounded, the other goes to the tach which has a power and ground...
*EDIT*
Did a bit more research, it appears that they used this IP mounted engine speed sensor for the tach for the entire run of the Tempo/Topaz diesels..
It may still be worth grabbing the tach as it appears the speed sensor is a standard ole magnetic pickup.. Chances are there is a "toothed wheel" or "slotted wheel" in the IP.. if you can find out how many teeth/slots it has that could be worked with to make the tach useable on anything...