Here are the two plug variations on the electric speedo.
http://cleanflametrap.com/speedo.html
I am currently trying to figure out why mine is not working. The wiring diagram don't show the black ground that have been mentioned in a few of the posts. I'm heading out in the garage to try that out right now.
What car are you going 2.4 on? I just got my '81 up and running (minus the speedo working). I might be able to assist you in some wiring questions.
edit:
Speedometer is now working! The speedo was not properly grounded!
Also of note,
the switched power for the cluster cannot be fuse #5 on older k-jet cars. This fuse is hot all the time. There is a distinct break/gap in the fuse panel further down, the fuses are switched after the gap. So power for the cluster needs to come from the lower section.
There are two different wiring layouts for the plug, like linked to above. If the plug has a blue, green/white, and black wire: The
blue is switched power for the entire cluster! (otherwise your warning lights are on ALL THE TIME, if not hooked up the cluster will not have power), green/white is the power from the cluster to the sensor, and black is grounded (for both the sensor and the cluster).
If the wires are red/black, black, and blue: then red/black is power, black is ground, and blue is power to the sensor.
Another thing I found: Some clusters have the green/white and black wires switched. I had mine as in the picture above, but the speed was way off and the needle was jerky.
I put the green/white in the middle spot and the black in the lower location, and all is good now. Power remained in the same location.
Sensor wiring: Run the power from cluster to speedo sensor (Blue or green/white depending on plug), then run the other terminal of the speedo sensor to ground. I used the ground on the drivers side of the center console.
I'm going for a drive in a day or two. I can't wait to blow the cobwebs off, it's been to long!
Thanks for the info in this thread everyone!