Trying to wire up a monster tacho onto a 300zx have red black and green wires where do they go

you have an in cluster factory engine tachometer (RPM)?
the tacho is meter in the cluster and does not use speedo parts or its cable.
its just a meter that needs power, ground and spark tacho signals
if all 3 are good, the meter is bad. period.
the tacho signal goes to the ignition coil minus lug, and will good, as engine runs. so... wires bad, to tacho or tacho bad.
ever price a new one? or even used? $100 used?
you willing to pay that much for just a factory tacho?

there is NO speedo cable. this old 93 is electronic, (rare on most 93 cars made, toy is advanced)
here is the proof, amazing how books dont lie....
there is a speed sensor.
the tacho and speedo use the same power and ground
leaving just one wire,r-g red-green RPM sig. pin 5 of cluster
an is SPARK primary sig. so if only tacho is dead.
then the tacho is bad, or that pin 5 wire is dead.
got you to just 2 possibles.

The green wire is always a ground you must ground it

Assuming red is positive, black is negative or neutral the green is usually an earth wire and should be mounted to the cars frame.

your tacho should have 4 wires 1 black =ground 2 green=ignition 3 white/black =ignition coil contact breaker side 4 red=illumination make sur your tacho is for the correct system ie. pos or neg ground

to wire a tacho red - positive
black - neg
green - negative of coil

Hope this is what you are looking for and hope it helps....Good luck.

1984-89 Nissan 300ZX Stereo Wiring Constant 12V+ Red/Black Switched 12V+ Blue Ground n/a Illumination Red/Yellow Dimmer n/a Antenna Trigger Green/Black Antenna Left Rear Front Speakers 6 1/2" Doors Left Front (+) Blue/White Left Front (-) Blue/Yellow Right Front (+) Brown Right Front (-) Brown/White Rear Speakers 6 1/2" Side Shelves Left Rear (+) Red Left Rear (-) Green Right Rear (+) Blue Right Rear (-) Pink

if its a monsta tacho red wire to ignition in fuse panel black to earth in engine bay green to negative wire on coil if you have ecm there will be a tacho wire on points cover check that it dosent have power and that should be the one

at idle ,if the tps is adjustable,with slotted screw mount holes,,while at idle move tps(with screws loose )untill idle sounds about right ,then tighten ,with out rpm meter hard to adjust just right ,but not crittical

The sell a nifty little invention at Wally-World. Its called a wire harness...look for it in the auto parts section. it will wire directly to your stereo wires and then just plug & go... if your subaru wires are missing the harness on the end, its a whole different ballgame, and its gonna be fun...try this...

Car Radio Battery Constant 12v+ Wire: Blue/Yellow
Car Radio Accessory Switched 12v+ Wire: Yellow/Red
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Green
Left Front Speaker Positive Wire (+): Brown/White
Left Front Speaker Negative Wire (-): Green/Black
Right Front Speaker Positive Wire (+): Red/Yellow
Right Front Speaker Negative Wire (-): White/Black
Left Rear Speaker Positive Wire (+): White/Red
Left Rear Speaker Negative Wire (-): Red/Green
Right Rear Speaker Positive Wire (+): Blue/Green
Right Rear Speaker Negative Wire (-): Red

Let me know how it goes!

its the red and white wire behind the guages