[maxbell]

I recently put a V8 in my 74 Mustang II and purchased a used tachometer off ebay for a V8 but still does not work. Any ideas?

[Harrison_06]

do u have tha tach wire goin to tha postive side of tha coil?

[maxbell]

I do not know for sure where it is going as there is only the original wiring which I put back as removed from the 4 cyl. coil and it worked before the swap. I will try to get a wiring schematic to find out how the tach is wired in. There is something about a different color adapter on the back of the tach for a V8 so I purchased one of them but to no avail.

[Cobra351W]

One wire goes to the coil, another goes to a ground, another goes to the power.

[maxbell]

I should probably be more clearer on the type of tach I purchased off ebay. It is an factory original in-dash unit. However there is an attachment on the back that supposedly is required to convert signal to v8 perimeters so the tach will be accurate, any way it did not work. I tried the unit on both the tach that was in the car when I bought it,(which was for a 4 cyl. and did not have the attachment and worked fine),and the tach that I purchased off ebay to no avail. Does anyone know about the attachment on the back of the original tachs and how to check them out or where to get them?

[maxbell]

Well I found the problem. I was removing the dash for my nitrous wiring and found a wire off the ignition switch. After replacing the wire the factory tach for the V8 WORKS !!!!!!!