Cluster plug grounds
 

Quick question, chasing cluster issues, I just want to make sure that everything is grounded that needs grounded. I went through and tested each pin in the cluster plug and noted which ones were grounds. So my question is, are these all the grounds associated in the connectors? (Grounds marked with green dot) thanks!
https://cimg0.ibsrv.net/gimg/www.rx7...a6dff49f9.jpeg

All those green are definitely not all grounds. Good rule of thumb is if it's red, or red w/ stripe - it's not a ground.

hmm well that alarming. Lol! I guess let my clarify I’m checking correctly….multimeter, continuity setting, probe on pin, other probe on vehicle ground, in my case, using the dash bar behind the cluster.

Grounds for C1-01 connectors are 1E, 4K, and 4H. (In a 94). Most of what you have highlighted are the illumination sources for the dash lights, high beam indicator, and turn signals. By putting your meter on a hot line and the other to chassis ground you're essentially just bypassing the cluster with 12V, so of course its going to read continuity, it's a short circuit. Your dash bar is now confirmed connected to the negative terminal, good info to confirm.
To check continuity in the cluster, you should have the black probe at the corresponding ground in the cluster, and the red probe at the corresponding input - testing the connection through the cluster, rather than the wiring.

What are the cluster issues? Can start looking at specific pins and wires based on the issue. If it's the flexible printed board or and individual board for a gauge, you may be in for a digital dash unless you're really good at small connection soldering/desoldering.

Ohhh that makes a lot of sense. Still riding the learning curve to the electrical troubleshooting realm. Problems are, switched to a haltech 2500 with plug and play harness, speedo, tach and oil pressure do not work. Not too concerned about the oil pressure, I have a CAN gauge for that. I’ve verified ac current coming from the VSS and continuity to the cluster connector, and tach is hooked up and programmed correctly and also shows continuity from haltech to cluster connector. Cluster was refreshed by Gagne about 2 years ago, with probably about 300 miles driven on it since then.

AC on the VSS? I haven't looked into the Haltech but I'm pretty sure it's all DC in the car (aside from inside the alternator).

If VSS = Vehicle Speed Sensor, then yes, it is an AC sine wave signal. The sensor is a variable reluctance (VR) type sensor similar to the CAS, and it produces 8 pulses (or zero crossings) of the sine wave for every 1 full rotation of its shaft. On this schematic from the '93 Service Highlights manual, the "generator" is the VSS


https://cimg8.ibsrv.net/gimg/www.rx7...52f8523757.png

Hey look at that! Learned something new!

Are you using the correct wiring diagram?

Do the wire colours line up correctly with the diagram?

RHD may have different wiring.

For instance the four plugs at the back of the gauge cluster connect to the instrument harness in different configurations*.

Version 4~6 RHD can have considerably different wiring.

Wiring can differ between Manual and Automatic as well.

(* of the four plugs two connect to the cluster by a short harness and two are direct connections from the instrument harness. For some reason at least one plug of each set of two is swapped from the short harness to the direct connection and visc-versa.)

Best to trace back the wires in the wiring diagram to see if they run to grounds. My vague recollection is that out of the four plugs there are only two wires that run to grounds. But again best to check the diagram;.

You can likely find the JDM wiring manual specific to your version of car here:

(password is embedded in the file name. File is massive maybe 400 MB)

https://www.dropbox.com/sh/4s3ydox2z...3v2Zr4xRa?dl=0

Looking at the Version 1 JDM wiring manual there are only two wires running out from the plugs directly to grounds. 4H (black) runs through the "I2" (short) harness and "I" Harness to ground "3". 4K (black) also runs out the "I2" harness, but connects to ground "3" through the Front (F) harness.

Other wiredsrun to ground through devices that are connected to unspecified grounds.

Except wire "1E" runs to ground "2" by connecting through "I2", 'I", "D" (dash harness) and "EM" (emission harness - sometimes called "engine harness")

And wire "4J" (broiwn/yellow) runs through to ground "2" through the brake fluid level sensor passing through I2, I, and F harnesses.

This is for RHD Version 1. Version 2 & 3 are likely similar. Later versions could be different.

For automaitt there is a a wire from 5K through "I3" and "I" to ground "3".

I guess I never paid too much attention to the finer details! I had a few pins match up in the colorings at least. I never thought to check the rest. I’m mainly concerned about the tach and speedo, which seem to line up with what’s on the diagram posted. The ECU gets its speed signal from the R/G wire next to the two for the VSS, which my understanding is a cruise control signal? I’ll definitely cross check the plug pinouts and see how they differ.

This might not be the exact schematic specific to your FD (it's a '93 USDM FD diagram), but for the purpose of understanding grounding paths it should be helpful. Per the diagram, the path I highlighted in yellow is the main ground path for the speedo, odo & tach. Note that that path is rather convoluted, and traverses several harnesses in the car - EM (emissions), F (front), D (Dash) and I (Instrument) harnesses. So a break anywhere along that path would result in the tach/speedo/odo seeking an alternate route of least resistance, which are annotated in green highlight.


https://cimg9.ibsrv.net/gimg/www.rx7...d88dbe4234.png

If your running an aftermarket ECU that did away with the EM harness, you most likely lost this ground path (yellow - to pin 1E).

that’s great to know, and very helpful actually lol I actually got them to work! I traced all the wires and grounds and everything seemed as it should. So I just put everything back together and as of now it’s working! The ONLY difference is, prior to this I did not have my combination lights plugged in bc the bumper was off. Now they’re plugged in and everything is good! But I wouldn’t think they would have anything to do with each other?