Dixco Hood Tach Wiring Help

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MrFollmer

MrFollmer

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I bought a replacement Dixco Hood Tach for my 1965 Dart 270 Conv. Yes, I know...it’s not original, that’s not the point.

Old tach had four wires, new tach has three. I have four wires coming through the hood.

Can anyone offer a color to color combination to help me out? Photo for reference below. I’m thinking:

Black to Black
Both Reds to Red
Gray to Green.

Thoughts?

22369FB9-E73E-40A1-9B25-3AB948313DF4.jpeg


E3D100EF-3D06-422B-9009-5C121C9B4C70.jpeg
 
More important- what are the four wires doing? I can see one wire for power, one wire for signal, one wire for ground and maybe one wire for light. Understanding what the 3/4 wires do and then the color code doesn't matter.
 
Murray said:
More important- what are the four wires doing? I can see one wire for power, one wire for signal, one wire for ground and maybe one wire for light. Understanding what the 3/4 wires do and then the color code doesn't matter.
Click to expand...
I have no idea what each does.
 
You will need to trace the four wires from your car back to their source to understand what they are doing. Then you will understand why your new tach only has three wires. Perhaps your new tach has eliminated the ground and made it ground to the case.
 
So I confirmed this:

The gray wire is attached to negative side of coil. So it must pair with the green. See photo of dixco box below.

Black “should” be ground. So black to black.

My issue is the second Red. Box says “switched 12 volts” which is Greek to me.

image.jpg
 
This is good. " Switched" means the wire is only hot when it is switched on. In other words, when the key is turned "off" or on "acc" there is no power present, it is switched off. So your red wire is hot (or switched) when you turn your key to "on" or "ignition". This wire powers your tach only when the engine is running. Your green wire from the coil is supplying the signal that allows the tach to give you 'RPM"s. The only mystery remaining is what is that fourth wire for? Maybe your new tach doesn't have a switched light wire (needing a separate wire, switched) but has a light that is on constantly when the tach is on, not needing a separate wire. Sorry to be so "wordy", hope this helps.
 
^^THIS. Fourth is likely the lamp which can go to the dimmer controlled dash lighting if you so want it to. This is the orange bundle coming out of the fuse panel from the "INST" fuse on one end of the panel.
 
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