Help...two hours and still nothing on the tach

[mally002]

I have spent over two hours in the cold garage trying to get my tach working, I searched the board, downloaded diagrams, jumped wires, tried old coil and still nothing. I even bought another tach, but both tachs don't even budge, they are DEAD....so it's got to be a wiring issue....right?

Here's the scoop,

1970 240z with pertronix and no resistor. (See photo 1 of current hookup)

Tried different configurations and then pulled out my old coil with resistor and still both tachs don't register anything, like they are not getting any signal at all.

Started looking at the wires and noticed a black/white wire that was cut and pushed up under the lip. (see photo 2). Does this wire figure into the tach?

Started to check the wires and the green/black, black/white and solid black wire appear to register hot when checking from the connector block inside the dash. (see photo 3)

I'm assuming the tach just simply plugs into the block (see photo 4, which goes right into photo 3) but plugging in produces no result.

I've tried jumping different wires, doubled checked the wiring diagrams I downloaded but everything I try comes up with no result, not even a blip on the tach, the needle just sits at the bottom and never moves.

Could someone with a working tach with pertronix and no resistor please tell me exactly how yours is hooked up, wire colors and where they go ect....or if you have a picture please post it.

I'm going to be out here working the rest of the day so if you have any suggestions please post as I will be checking in every 30 mins or so.

Many thanks,

Randy

PS..just looked at the wires again to be sure and it looks like there are two black/white wires coming from the same area of which one is cut (photo 2). So going into the coil are the....Red, Green/White, and the Black/White on the + side and the solid Black going to the - If that is correct, my tach still doesn't work. Is it the mystery wire, or is my wiring all screwed up.

Edited December 2, 2010 by mally002

[EScanlon]

No, you've finally found the TWO Black/White wires. Both need to be in the circuit for the tach to operate.

Connect the tach with the plug, you don't need to insert the bulbs at this time, just the 4-wire plug.

Insert the key in to the ignition and turn to the RUN position.

At the coil, identify WHICH ONE of the two B/W wires is receiving 12v+. Once you've identified it, connect it to the G/W wire.

The OTHER B/W wire goes to the Positive (+) terminal on the coil.

The Black wire goes to the Negative (-) terminal on the coil. This Black wire should have continuity to the black wire at the distributor (that's how you can check to see it's connected properly).

Start engine, check the Tach.

You don't need the resistor. It normally gets mounted between the B/W that's hot in the RUN position and the G/W wire when you are using points.

FWIW

E

[EScanlon]

I vaguely recall that the Red and "a" black wire come from the Pertronix unit and get connected to the coil, but I need to check on that.

E

[mally002]

Enrique,

Your a genius!!!!!

It works perfectly. Thank you, Thank you, Thank you............

Also thanks in advance for taking a look at my plastic pieces, they should be arriving soon.

Regards,

Randy

Edited December 3, 2010 by mally002

[EScanlon]

You might check with others as to running the original coil with the Pertronix WITHOUT the resistor.

When I hooked up the Pertronix in my Roadsters I used the resistor and did not notice any problems, but others may have opinions that might vary.

I mention this only because some folks have commented that their coil ran HOT! due to the 12v continuous feed as opposed to the 6-8v when powered through the resistor.

I did get your pieces today and I've already sent you pics of what I received and a description of each.

Glad this got your tach working.

FWIW

E