tach install problems

[cobra50]

I am trying to connect my tach and tach adapter up, but im having a problem.
The tach powers up but does not show any RPM's. I did a search and tried every way I found, like the red wire under the hood or the green wire under the passenger side kick panel. What could be wrong or is their another way? :shrug:

 

[cobra50]

tach problem

Is it possible that the adapter is bad?

 

[cobra50]

wiring

I was also told by a local performance shop, that you can go directly to any coil. cut the power wire in half and one side of it goes to the red wire and the other goes to the red/green wire. does this sound right?