66 c10 tach wire

[Afirehawk1]

Got 2 wires. Pink and brown from harness.
Does it matter which goes to which terminal?

[ray_mcavoy]

Yes, it does matter which wire is connected to which terminal.

Viewing the tach from the back, the terminal on the right side should be marked "coil". The brown wire should be connected to this terminal. And the other end of the brown wire should be connected to the negative (-) side of the coil (or HEI "tach" terminal).

The terminal on the left rear of the tach should be marked "12V". The pink wire should be connected to this terminal. And the other end of the pink wire should run down to the fuse box and plug into a terminal (on the right side) that is live with the ignition on.

The tach also requires a ground connection and that is made through it's metal mounting plate which is screwed to the grounded metal cluster case.

[Afirehawk1]

Originally Posted by ray_mcavoy

Yes, it does matter which wire is connected to which terminal.

Viewing the tach from the back, the terminal on the right side should be marked "coil". The brown wire should be connected to this terminal. And the other end of the brown wire should be connected to the negative (-) side of the coil (or HEI "tach" terminal).

The terminal on the left rear of the tach should be marked "12V". The pink wire should be connected to this terminal. And the other end of the pink wire should run down to the fuse box and plug into a terminal (on the right side) that is live with the ignition on.

The tach also requires a ground connection and that is made through it's metal mounting plate which is screwed to the grounded metal cluster case.

Then i got it right! Thanks for helping

[Afirehawk1]

Originally Posted by Afirehawk1

Then i got it right! Thanks for helping

Ok finishing things up

If brown goes to the negative on the coil
Where does the white go? It is label coil as well
This is using the American Auto Wiring harness

I am using a Tach conversion harness
Pink and brown wiring

[Afirehawk1]

Originally Posted by Afirehawk1

Ok finishing things up

If brown goes to the negative on the coil
Where does the white go? It is label coil as well
This is using the American Auto Wiring harness

I am using a Tach conversion harness
Pink and brown wiring

Any suggestions

[The Rocknrod]

You know what the tach wires need to be (from ray_mcavoy's post), the question is what does American Autowire say the white one is From and To? Without theyre wiring diagram, which you should have we'd be lost.

[Afirehawk1]

Originally Posted by The Rocknrod

You know what the tach wires need to be (from ray_mcavoy's post), the question is what does American Autowire say the white one is From and To? Without theyre wiring diagram, which you should have we'd be lost.

The diagram says the same
Connect to the negative side of coil
Just wanted to verify

[ray_mcavoy]

Originally Posted by Afirehawk1

If brown goes to the negative on the coil
Where does the white go? It is label coil as well
This is using the American Auto Wiring harness

GM changed the color code on the tach signal wire from brown to white sometime in the late 1970's. Since you said the white wire is also labeled coil, it sounds like AAW is simply using the newer GM color code for the same wire.

[Afirehawk1]

Originally Posted by ray_mcavoy

GM changed the color code on the tach signal wire from brown to white sometime in the late 1970's. Since you said the white wire is also labeled coil, it sounds like AAW is simply using the newer GM color code for the same wire.

Ok
so both wires get connected to the negative side of the coil?

[ray_mcavoy]

Originally Posted by Afirehawk1

Ok
so both wires get connected to the negative side of the coil?

No, you only need to use one or the other (not both).

I think you have ended up with two tach signal wires (one white and the other brown) as a result of the wiring harnesses you are using.

If you're using the Classic Update wiring from AAW, I believe that includes a tach signal wire (white). That wouldn't have been present in the factory engine/cab wiring.

And since the factory engine/cab wiring didn't include a tach signal wire, they put that in a separate 3-wire harness (brown signal wire along with a pink power wire and a gray illumination wire). It sounds like the tach conversion harness you bought is basically a duplicate of this.

[Afirehawk1]

Originally Posted by ray_mcavoy

No, you only need to use one or the other (not both).

I think you have ended up with two tach signal wires (one white and the other brown) as a result of the wiring harnesses you are using.

If you're using the Classic Update wiring from AAW, I believe that includes a tach signal wire (white). That wouldn't have been present in the factory engine/cab wiring.

And since the factory engine/cab wiring didn't include a tach signal wire, they put that in a separate 3-wire harness (brown signal wire along with a pink power wire and a gray illumination wire). It sounds like the tach conversion harness you bought is basically a duplicate of this.

Ok
Since the tach harness (pink and brown) are connected to the back of the tach itself, i should just use the brown wire to the coil and tie off the white?

Want to make sure i got this straight

[ray_mcavoy]

Originally Posted by Afirehawk1

Ok
Since the tach harness (pink and brown) are connected to the back of the tach itself, i should just use the brown wire to the coil and tie off the white?

Yes, that would work.

Just leave both ends of the white wire unattached to anything. Or it could be re-purposed for something else if needed since you already have the brown wire for the tach signal.

[Afirehawk1]

Originally Posted by ray_mcavoy

Yes, that would work.

Just leave both ends of the white wire unattached to anything. Or it could be re-purposed for something else if needed since you already have the brown wire for the tach signal.

Great
Thanks for helping