What wire is negative and what is positive?

[GiRlsGoFaStEr]

So I have a 99 eclipse rs-t and i recently installed my new Autometer tach. I know that the rpm's wont work correctly if I dont install the Msd Dis-Tach Driver, so Im in the process of doing that, but I have downloaded the diagram from the msd site to put this into my coil harness and it is telling me to match colors to my harness that I dont have the same colors for. The Dis Tach Driver has a grey wire (which goes to the green wire on the tach) a black for ground, a red/green (for the blue black on the eclipse coil harness) and a red (for a black white wire). Well inside of my Coil pack harness, I have a green/black wire, a pinkish brown looking wire, and a red/black wire. Anyone know which wires In the harness are for negative and posotive? I know its confusing but Im thinking the green/black would be negative, but I dont want to try it unless I know for sure. Thanks in advance.

 

[GiRlsGoFaStEr]

Also I forgot to mention I have a 420a engine. I still can't find the answers anywhere on the site. Im sure someone has installed a tach and could try to explain which wire from the 420a engine coil wires are negative and posotive. Thanks

 

[luv2rallye]

I haven't installed a tach on the 420a but I do have the '99 factory Mitsu service manuals. If you still have the N/T harness/coil setup, it shows a harness black/red to be constant +12V, and brown & black/blue wires to be the two firing (negative) wires going to the PCM. I suppose you could connect to either of those two but the factory tach is connected to PCM pin 73 (white) and also to Automatic Compressor-ECM pin 3 (brown).