Coil Negative

[Jforce]

Hi,

I want to connect an aftermarket tacho on my 95 K8 V6 mx-3.

Now everyone says that u need to use the red wire closest to the front bumper on the 3pin plug.

However my wiring is differt.

from front bump to rear:

Blue
Red
Yellow/Blue

so i tried connecting it to the blue wire, Rpm stays @ 0

Tried hooking up to the other 2 wires and the gauge goes nuts. Not a steady signal but going from 500-3000 @ idle.

Switch on gauge is set @ 6 cil.

Any suggestions?

[umcamara]

If you have a test light, just probe the thin-gauge wires at the distributor for one that flashes the test light rapidly. It's AC, that's why the test light flashes.

**Edit: It should be a yellow with blue stripe wire.**

[Jforce]

The yellow/blue should be te tacho signal yeah, but the manual says connect to coil negative which should be the red wire..

but either way all wires aint working. I cant get a solid rpm rate. The original tacho works fine (so i dont actually need it, but its fun with the shift light and digital numbers).

dont have a test light, but i do have a multi meter. does it matter wich kind of wire u use? I've used 1mm 12v wire.

[umcamara]

The yellow/blue should be te tacho signal yeah, but the manual says connect to coil negative which should be the red wire..

but either way all wires aint working. I cant get a solid rpm rate. The original tacho works fine (so i dont actually need it, but its fun with the shift light and digital numbers).

dont have a test light, but i do have a multi meter. does it matter wich kind of wire u use? I've used 1mm 12v wire.

Negative coil is usually considered tachometer signal.

[Jforce]

okay, maybe i can connect the wire behind the instrument cluster?

[umcamara]

okay, maybe i can connect the wire behind the instrument cluster?

One wire goes to the tach signal

One wire goes to ground

One wire to a switched 12 volt source (ignition)

Usually one wire to dash lights for illumination.

Shouldn't be difficult. You should have a testlight before attempting any wiring jobs, they're cheap enough. Never just go by the wire colors that others tell you.

[Jforce]

yeah i know it should not be difficult.

my tach has 3 wires

1 for 12v source
1 ground
1 signal

so i looked in the manual for the correct wire, wich should be on the 3pin plug.


I tried ALL 3 wires, but it is just not working.

1 of the 3 should work because 1 of the 3 IS the tacho signal.

I don't understand it should work but somehow the signal is screwed.

[umcamara]

What did you connect the 12 volt and ground wires to?

[wytbishop]

This is why we put a 1K ohm resistor in the tack input wire when doing the HEI mod. You have the right wire, but there is too much current getting to your tach. That's why its going crazy.

[Jforce]

12v is connected to a igniton on source.

ground to body just under the A-pillar.


so i have to buy an 1000 Ohm resistor and put this between the coil negative and the signal wire of the tach?

[umcamara]

12v is connected to a igniton on source.

ground to body just under the A-pillar.


so i have to buy an 1000 Ohm resistor and put this between the coil negative and the signal wire of the tach?

Yep, Wytbishop is right on there. I can't believe I never thought of that...

[Jforce]

hehe, okay il try this.

now i only have to find the correct wire, as my 3pin plug is colored different than other mx-3's.

see if i can find a test light.

[umcamara]

hehe, okay il try this.

now i only have to find the correct wire, as my 3pin plug is colored different than other mx-3's.

see if i can find a test light.

It should be the yellow with blue stripe wire on the 95 GS. If you set your multimeter to AC that wire should register a voltage.

[Jforce]

by the way, im not doing an HEI mod (yet), so the stock Ignition Coil has already an 1K ohm resistor build in. Right?


yes but that signal is interrupted. And the guys from my mx-3 club say it should be wire B on this diagram:



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which is the Red wire.

[wytbishop]

So in that diagram...the wire which is labeled "Tachometer" and shows a resistance in the circuit doesn't strike you as the correct wire?

The one labeled "C" in the 3 pin connector?

I'm just throwing it out there...I'm no expert.