2G 2g Electrical issue. Some dash gauges not working

[rbeccari56]

I own an early 95 GSX auto that I have been slowly working on for the last 21 years. It's ready to drive but I am currently experiencing a gauge issue. The tach, speedometer and the fuel gauge aren't responding. I already replaced the cluster with no results. I tried 5 different power units, with no change for the tach.

I upgraded the fuel pump wiring, pulled the fuel pump assemblies (both sides) cleaned all the contacts with no results. Also removed the speedo harness at the tranny, cleaned the contacts also with no results.

The thing is that several years ago, everything was working fine. Searched the forums, but never really found anything related to this. I'm running ECMLink V3. Is there maybe a setting that can turn these gauges on or off? I'm at a loss. There is no common thing except for the cluster (which I already replaced once with the exact same results) I don't remember changing any one thing between when everything worked to now.

Any clue, hint or suggestion will be highly appreciated. Thank you for any assistance.

 

[steve]

What exactly have you checked or are you just swapping parts?
Do the various lights in the cluster work? The are powered from the taillight relay.

Most of the gauges are powered from the 10A fuse #8 in the Junction Box. It gets power from the ignition Switch IG1 circuit. The Brake, Oil, and Fuel warning lights also get power from the same fuse.

The ground connection is shared by the gauges and the ODB2 connector, it's ground #5. The warning lights use various grounds that are connected to the sensors for the lights.

 

[rbeccari56]

Thanks for the input. Forgot to say that the fuse is fine and all other gauges and light are working. So it's just the 3 specific ones that are not. I've been chasing this issue down now for over a year, with no luck. Never tested the taillight relay, so thats up next.

 

[steve]

As mentioned the taillight relay is only powering the cluster lighting. If it lights up when you turn on the headlights that part is fine.

I'll look again to see if there is anything only tied to those three gauges when I get home.

 

[luv2rallye]

Does your rheostat (dash light intensity) also not work?
According to my 1999 wiring diagrams, the common thing between all those things you mention (and rheostat) is the grounding which goes through the junction block connectors B-66 pin 2, B-49 pin 1, to the chassis ground point #5 (under dash left of center duct - pic is unclear but may be behind instrument cluster).