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Tach wiring

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I'm trying to diagnose why my tach doesn't move (I know it functions, because I bench tested it), and I think I've discovered why.

In the photo below there are some wires cable-tied together (at the right hand side of the picture) - a pair of black wires ending in a spade connector, and a single black wire, with a yellow-ish sheath, ending in a spade connector.

8403001857_526a8aa4c8_b.jpg

From my reading of the circuit diagram, the sheathed wire should be the wire from the tach.

My car has a non-points electronic system inside the distributor (perhaps Pertronix, I don't know).

Where should I connect these wires/spades? I did a search, but am not sure what I found exactly applies to my situation.

Thanks!

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The tach signal wire connects to negative terminal of the coil.

It should work fine with the Pertronix.

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which means the black wire is not attached to coil - question is, does the black wire on right go to tach, or to coil? You need a black wire from coil leading off thru firewall.

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Upon reflection, and more coffee, there was a recent tread with same question. There appear to be two wiring versions which accomplish the same thing. In your case, I suspect wire comes from tach, went to dist first, and then to coil. It was disconnected for Pertronix. But PO may have disconnected black wire from coil too. That's what you need to look for, and leave wire on right where it is.

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Upon reflection, and more coffee, there was a recent tread with same question. There appear to be two wiring versions which accomplish the same thing. In your case, I suspect wire comes from tach, went to dist first, and then to coil. It was disconnected for Pertronix. But PO may have disconnected black wire from coil too. That's what you need to look for, and leave wire on right where it is.

Thanks, Hans. I'm still not quite sure about what the wire pair was attached to - not the distributor, but perhaps a capacitor/condensor? What I will try is attaching the single black wire (with the yellow sheath) to the -ve side of the coil. I should really get my multimeter out and check that wire for voltage before doing so - it shouldn't be live if it's the signal wire from the tach.

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It would have been attached to a blade terminal on the side of the dist. that went to condenser and points. The Pertronix replaces all of those, including the wires to the coil. I think in your case, one of those black wires goes to tach, the ether goes to coil. I also think the coil end was disconnected, so no link between coil and tach. See if there is a loose black wire under the coil.

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(edited)

If I may hijack this thread, I am a little stumped. I have a 73tii that was running points, and I installed a pertronix unit. The car started right up and ran great, but the tach didnt work.

I realized that I need to hook the black wire back up to the negative side of the coil for the tach signal, but as soon as I do this, the starter acts like a serious load has been applied to it. Looking at the wiring diagrams for a NA tii, there seems to be a little more junctions with the tach wire than on other models of 02's. Am I safe on running a new wire from the tach directly to the negative post of the coil?

 

Thanks

Rob

 

[Edit]: I figured it out thanks to another post. The timing was set too far advanced! Sorry for the unnecessary post!

Edited by RobC

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