ok just bought a tacho im an absolute dummy with electricals have instuctions but still have no idea really on where to wire up power (red wire) & white wire ive read some old threds gave me bit of ideas but still not real confident on wat im doing can someone point in the right direction, please. if i post a picture of all the wires under my dash will it help to explain?

can i hook power up to here?

What wires do you have ?

Normally there are 3 OR 4 wires.

http://www.centuryperformance.com/mallory/wiring.asp

Red to 12-volt "switched" power supply
Black to ground
Green to trigger (negative side of coil, or tach output terminal if using an aftermarket ignition control)
White (or yellow) to light circuit

thanks dude its ok now i bit the bullet and just hooked up wat i thought would work and it did (touch wood) should be ok now, thanks!

I'm havin issues with this at the moment as well, all connected up as dattodude said, but no action. I got lazy and didn't connect the light, & figured that that may somehow be the problem so (still being lazy) I attached it to the switched power so that it was on the whole time when the ignition was on. Still no luck. The guy from Speco recons that it 'must' be attached to the light circuit, but I can't see how this would make a difference.
any lectricians out there who can tell me how to test for signal from the coil?
or test to see if the Tach is ok?

most after market tachs have a 4-6-8 cylinder switch that could be the key might have to take the cover off the back side.

Quote:
Umm does the engine run?
If thats to technical to test. Easiest method is, grab a mate. You lean into engine bay, take the ignition coil lead out of the dissy. Hold the end of the lead in one hand and put your other hand on the motor. Next ask your buddy to crank the engine.
( make sure the car is out of gear, always think safety first ). If you feel a small tingle, the coil negative is receiving the correct signal.

Thanks Phunk, I knew I could count on you.

I was thinking more along the lines of using a multimeter or something. But if its as simple as engine running = good signal, then I spose I have good signal.

Hey Phunk, your smartarse remarks actually helped on this one, so cheers bro!

I took the tacho out and over to the trusty parts chaser (86 'rolla) and hooked it up in a half @rsed way, by wedging the + & - into the battery terminals and holding the green wire onto the coil -ve. It worked fine, but when I went to give the throttle a blip, I got a little nip from the coil- not a full charge, just a quiet 'hello'.

The datto didn't do that when I had tried the same thing. So I got out the manual & checked the wires to the coil- turns out that they had been hooked up the wrong way round for years (or at least since before I had the car) because the red terminal was on the black (-ve) wire and the blue terminal was on the +ve. When I hooked it up I assumed that red ment + & blue meant - ve. Spun me out that it still worked with current running the wrong way through it

Anyway the tach has signal- doesn't work that well, but it does have signal.