Charger Specialties Repro Tach

[HDCharger]

Took my 73 SE Dash out and put in the new tach, raplaced the dash and it didn't work.  I thought OK I knocked the wire off when installing.  Out comes the dash again.  Wires are on so I check to make sure I am getting 12V.  I have 12V to the tach and the other wire is going to the negative on the coil.  Still doesn't work.  Any suggestions? 

When I turn the ignition key to on the Tach goes to zero but when I start the car it doesn't move. 

[HDCharger]

OK.  The tach needle will move to about 800rpm when idling and then when I increase the RPMs the needle moves in reverse.  Any ideas what is going on here?

[NMike]

do you have MSD? is there a good ground?

[HDCharger]

I have the stock electronic ignition.  I will double check the ground to the instrument cluster.

[CHRGR SE]

Any resolution?

[HDCharger]

Not Yet.  Homestly i have been too busy.  I am going to try and get on it in the next couple days.

[71charger_fan]

What was the final outcome of this? I hope I didn't just throw a couple hundred bucks down a hole by ordering this tach.