Gauge cluster lights inop please read.
 

Please help, Yesterday I ran a ground wire from the negative terminal to the alternator bracket (please don't judge or ask) when I crank started the car the tach stopped working, it did move then went to zero, I shut down the car right away and removed the wire, and started the car again and the tachometer was working fine. Well this morning when I left for work the gauge lights did not work, I read here on the forum that I could jumper the white/green and red/green wire and if the cluster lights then its a switch problem. I jumped the terminals and the 15 amp illumination fuse blew, I did this twice.
All the lights are working interior and exterior except the gauge cluster, the two little indicator lights on the ac controls will dim when the switch is turned on, the indicator for vent control and recirc.

My question is, what is the next step, and why is blowing the fuse when I jump the terminals

Are you jumpering the W/G and R/G wires w/the headlight switch plugged in or removed? If its plugged in then unplug it and jumper the same two wires and see if the illumination fuse blows or not. If it doesn't then you have a short within the switch or you might have a short in the R/G wire.

I checked twice and made sure it was the W/G AND R/G wires, I did it with the switch out, so that should be out of the picture,, now I am :scratch:

If the switch is plugged in it does not blow the fuse does that mean the switch is not allowing current to flow, its only when I jump the terminals when the fuse blows. So if it is the r/g wire, should i just start checking voltage? not sure what to do from here?

The switch does prevent the voltage from routing from W/G to R/G. The R/G wire could be grounding out as a possibility. Take a multimeter set to continuity and place one terminal to the R/G wire and the other meter terminal to a ground and if the meter sounds then the wire is grounded (when it should not). And if possible, you try to get a visual of the wire to see if any obvious damage is apparent.

Thank you, I did notice that there was an aftermarket alarm wired in while I was checking earlier, and there was some splices that I removed and cleaned up, still did not help but was able to remove a awful mess of wires, I will keep this updated, and let you know the results, it may be a couple of days before I can get back at it. Again thank you for the help.

Do I need to do the continuity test with the switch plugged in?

Unplugged would be good.

What should I do next if there is NO continuity or a short in the wire? I will be checking tonight, I just wanted to know that the next steps may be so I can just run with.

I have checked continuity on the r/g wire and there is. I checked the harness from the switch to where it plugs into the main harness. I then check the main harness and it still has a short to ground. I pulled the illumination fuse and it still has continuity. so I am assuming that the short is before the fuse block or at the fuse block? What gets me is if I jump the w/g to the r/g it blows the illumination fuse (that is with the switch un plugged) if I plug the switch in and turn the lights on it does not blow the fuse. The switch has a constant power going through it (w/g wire) that when the switch is turned on it should allow power to flow through to the r/g wire(if this is the wire that is supposed to run the cluster lights). That being said why does the fuse not blow when power is sent through the switch, but it does blow when I jumper the terminals? I just want my freakin dash lights back.

If the R/G wire is tested w/the switch plugged in and the switch turned to the on position then the R/G wire should have voltage on it. If it does not then the wire is not receiving voltage and thus not blowing the fuse, as it's only when the wire is tied to W/G does it blow (thus the switch is not doing anything w/the voltage on W/G).

The R/G wire drops down from the plug that connects to the light switch and goes to connector FC-02 which should be up against the kicker panel (diver side). You can unplug it and test that initial segment og R/G to see if the short is located within that segment. If not then the short is later on in the wiring. FC-02 sends the voltage on the R/G wire to the dash lights and the cigarette lighter (problem could be there).

I did not get any further on testing the r/g wire it self, but I did decide to test the switch and found that I am not getting any power out of the switch at the r/g wire with the switch on. I will be getting another switch and keep this post updated from there.

You can damage the switch if you do not fix the problem w/the R/G wire.

I figured that ugggghhhh. I still need a switch, heck I need a wiper switch also, I will order both and get back to the wiring before I hook up the new switches. I will post the results once I find out whats going on, Thanks for all the help.
I wish there were better wiring schematics available.

Does anyone have any recommendations on getting to the main harness plug for the cluster, I want to disconnect the plug and check to see if my short goes away, if it does then I know its in the cluster harness FME-01 to ME-01 AND ME-02 or the cluster its self, but how in the heck do I get to it without taking half the car apart?

Have you checked FC-02?

That is the connector that runs from the wiper switch to the main harness? I will check it tonight.

It takes the harness w/the R/G wire from the light switch down to the front harness.

That was the first thing I checked, I checked from where the connector plugs into the switch itself, then I unplugged that section of harness and checked at the main harness with the switch harness unplugged, So I know its past the head light switch harness short section.

So, at FC-02 unplugged, you checked the front harness side of the plug and tested the R/G wire for continuity to ground to indicate the problem was within the front harness and not the headlight switch harness?

Correct the fault is not in the harness for the headlight switch, it is in the front harness, that being said, where does the fuse come into play in this system, I removed the fuse and still have a short to ground. I really appreciate all the help with this, you have been amazing with your responses.

The fuse is before the R/G wire so it is not a player here (remember, the W/G has the power from the illumination fuse and it is the role of the switch to transfer the voltage on W/G to R/G).

And the R/G wire on the front harness runs to FI-02 before it runs to the cigarette lighter illumination light. If you unplugged this connector and tested the R/G wire on the instrument side of the connector and the R/G wire found at the cigarette light bulb then a continuity to ground test could isolate that wire segment as being good or bad.

I think I have it isolated, I unplugged FC-01 and tested from the cig lighter illumination back and the short was gone, from that the other end back through the harness there is still a short. I currently have FC-02 and FC-01 unplugged, from FC-02 main harness side I followed the R/G wire through the harness, it actually meets up with another R/G wire that goes into one R/G wire and continues through the harness up through the dash that (then runs into the cluster and then over to the main side of FC-01). I could have my plug names mixed up here, but there is a blue plug on the passenger side of the column, when I unplug it and test for a short plugging my volt meter at the light socket at the cig lighter, the short is gone. So I thing I need to get to or behind the cluster to get to that part of the harness, but how the heck do I get there. I can see a white plug on top of a big metal brace that is above the steering column, but I cant get to it (I think that is FME-01)

What is an easy way to get to that plug. Ive got a gut feeling that my problem is in that FME-01 harness or the cluster itself.

Found it.
 

So my gut was right, it was in the cluster. I wish I would have pulled the cluster all along I suspected from the begining. Uggghhhh.
With the cluster un plugged their is no more short. I can jump the W/G and R/G amd let there be light. There is even 12v going to the cluster harness [12.7 to be exact per my volt meter] my question is do I try to repair this cluster. I do have a donor vehicle is a 1986 gxl that I could take the cluster out of a do not know if it is in working condition but it is worth a shot is there anything I need to worry about taking the cluster from the 86 and putting it into the 87 it is a early 86 build vehicle. So Early that the overflow jug was on the driver side strut tower.https://cimg4.ibsrv.net/gimg/www.rx7...92694e322e.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...a3382d9dc3.jpg
Please dont mimd the stanley screwdriver, Ot gets the job done :)

same difference

the cluster is probably repairable but you'd have to find out what got smoked on the board.

Found the problem.
 

The credit goes to a coworker of mine that is good with electronics. The problem was in two of the cluster bulbs. They had very low resistance, my numbers may be a little off here but you will get the idea. Most of the bulbs had between 30 to 40 ohms resistance, two of them were about 10 or 12 ohms. The low resistance was causing to much current to flow and when I would jump the wires, pop goes the fuse. I replaced the two bulbs - plugged in the cluster jumped the W/G and R/G wires and no blown fuse and the rx7 gods said let there be light. Even though I still have a switch problem I am super excited that it was just bulbs and not a fried board.