JMF 240 Posted March 20, 2021 Share Posted March 20, 2021 Hello, I have a '70 240z that I upgraded all my gauges on. I heard I needed to connect 2 of the 4 wires that feed the Tach together to make sure I complete the circuit when I replace it with a new (SpeedHut) gauge. Does anyone have experience with this and can help identify what two wires in the wire harness I need to splice together? Thanks, Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 20, 2021 Share Posted March 20, 2021 Post up the instructions for the Speedhut gauge. The white wire on the right of your picture, with the loop in it, is the one that the current passes through to the ignition system. It's the current that causes the 240Z tach needle to move. But there is also a voltage sensing tach that just has a wire from the negative post of the coil that terminates at the tach. You need to know what type Speedhut is using. Here's a bigger diagram than the tiny snippet you posted. https://www.classiczcars.com/files/file/1-240z-wiring-diagram/ Quote Link to comment Share on other sites More sharing options...
madkaw Posted March 21, 2021 Share Posted March 21, 2021 Follow the instructions for current type tach . It’s been too long so I can’t remember which ones it was . Quote Link to comment Share on other sites More sharing options...
JMF 240 Posted March 21, 2021 Author Share Posted March 21, 2021 Here are the Instructions from SpeedHut Tach. The issues I'm having is I lost power to the ignition. I have lights, blinkers, and the car will turn over but there is no ignition power. The issue I'm trying to figure out it how to complete the circuit loop that I seemed to have "broke" by removing the original Tach if that makes sense. I believe I need to connect the two wires on the other end of these two white wires (ones with a red band and one with a black band). Does this sound correct? Of course, I'll need to remove my dash again to get access to the original stock tach plug to do this. I will be connecting the single tach (yellow) wire on the SpeedHut gauge to the XDI Electromotive EMS. So I think I have that covered. I hope this all makes sense. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 21, 2021 Share Posted March 21, 2021 4 hours ago, JMF 240 said: The issues I'm having is I lost power to the ignition. I believe I need to connect the two wires on the other end of these two white wires (ones with a red band and one with a black band). Does this sound correct? Of course, I'll need to remove my dash again to get access to the original stock tach plug to do this. That sounds correct. If you know the colors you can just bridge them earlier in the harness, no need to get all the way up there. Unfortunately Nissan changes colors at the connections for some reason so the wires in the harness might not be white. Quote Link to comment Share on other sites More sharing options...
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