3" Tacho In Ke70 Flicking/maybe Reading Wrong

[roughjustice]

Hi guys.

I have an '84 KE70 (no tacho standard) and I bought a "DRiFT" 3" tacho just to jam in there so while I'm burning around in my 40kw I can watch the pretty coloured needle move up and down :)

My dad and I wired it up ourselves as per the instructions; Red wire to 12V ignition, Black wire to a good earth, Green wire to negative side of the coil, and White wire to dash lighting.

The lights all work fine, the power works fine (turns on with ignition only), but I'm pretty sure the tacho reading is wrong, and the needle also jumps literally 500rpm up or down in any given spot, it just flickers around.

We've tried wiring the RPM signal wire to the dizzy instead of the coil, didn't change a single thing. We also tried changing the earth, just running a wire straight out the passenger door and onto the negative terminal on the battery, also without any changes.

Also, it has a cylinder select switch on the back (4, 6 and 8). When it's on 4 cylinder, it idles on 2k rpm, and the reading is quite clearly wrong, because with a few short jabs on the accelerator the engine is apparently doing 11k rpm (11k from a 4k, I think not). When it's on 6 cylinder, it idles a bit lower but still too high, and again the revs are out. On 8 cylinder it idles on roughly 800rpm, so that's all good, but I'm not 100% on the revs when you actually use the accelerator. It seems pretty close from what I can tell, but I obviously can't tell for sure.

 

I'm wondering whether there's something we've done wrong with wiring, or whether it's just the fact that it's a $100 tacho and it's a cheap piece of shit.

 

Here's a video of the tacho at idle and the flickering with a few revs (set on 8 cylinder). Sorry about the phone quality, I'm not even sure if you can really see it, but it was the best I could do.

 

http://www.youtube.com/watch?v=7zdyLxmEK34

 

Any help would be greatly appreciated as it's rather annoying buying something, wiring it all up correctly and then having it do this. It's just a tacho so it's not the end of the world, but it'd be nice if it worked.

 

Cheers.

Edited February 22, 2010 by roughjustice

[KENut]

Make sure the contact points terminal where the black wire from the coil goes to the back of the dizzy, isnt shorting against the copper coolant pipe that runs alongside the head. Should be a bit of rubber hose over the pipe here to stop shorting.

My tacho was flicking like crazy because of the rubber melting, and therefore shorting through the pipe

[shauno88]

Hey guys, my Ke is doing the same thing! The copper hose was exposed therefore I put the rubber on that to. And it still does the same thing :(. Any ideas??