85 GT Gauge Cluster Wiring Questions

[Blownsob]

So here’s the short story....

I have a 1985 GT that I’m rewiring using the Ron Francis Express Wiring setup.

Specs-
Car 130A alternator and harness was setup for it by the folks at Ron Francis.

The MSD system is distributor, blaster coil, 6AL box, and tach adapter.

I have almost all of the wires for both pigtails on the cluster labeled with just a few questions.

Wires in question below:

-Black/Green 12v IVR wire - No idea what this goes to or what goes to it. It’s a solid core/single strand wire. Do I just give it a 12v source? That’s what makes most sense to me but I want to verify before I go hook up 12v to something I know very little about.

-Red/Orange and Yellow/LT. Green - These appears to come from the start/charge system and power distribution and go to the Ammeter.

-Dark Green/Yellow - Tach/coil negative, while in most cases I would know exactly what to do with this, I have no clue how this ties into the MSD tach adapter.

I’ve looked at the MSD diagrams and just can’t seem to make heads or tails of where the above listed wires go when using the tach adapter.

Any and all help you have would be greatly appreciated. Wiring is not my area of expertise and this is the last little bit I have to get figured out to make the car road worthy.

Thanks in advance!




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[Blownsob]

After looking further into it, I’m going to hook up the dark green/yellow which is the tach wire, to the msd tach adapter violet wire. That should take care of the tach. Then I’m still left with the two ammeter wires and the 12v IVR...


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[wraithracing]

The IVR is the Instrument Voltage Regulator. That is supplied with 12 volts and then IIRC it steps that voltage down for the instruments. I did exactly what you are doing to my 79 PC many years ago with a Ron Francis Wire Works kit, but I don't recall all the details. Besides there are some differences between how the instrument cluster pigtails are wired on the early cars compared to the later Four Eyes. Also my PC has the Voltage gauge rather than an Amp meter. Personally I wouldn't hook up the Amp meter. I have run a volt meter in the center console for some cars. Here is a great option that I will most likely do for some of my other Foxes when I get around to them. http://vb.foureyedpride.com/showthre...ash-Volt-Meter Good Luck!

[Blownsob]

Ah, that’s kind of what I was thinking but it was odd to see that single strand wire IVR. So I guess I can solder my stranded 12v ignition wire to it without any special precautions?

That then brings up another question though.. on the two pigtails on the back of the IC, each has a Red/Yellow wire that is labeled as a 12v source. Just seems odd there are so many 12v sources going to the IC. I was thinking there would be a “feed” for each gauge, common ground, and then the IVR, but those additional 12v source wires confuse me. I’ll have to look at the schematics again though as it may be possible they’re for powering the assorted indicator lights.

I appreciate your help!


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[Blownsob]

I do think I’ll probably just not worry about the ammeter for now. As long as I get speedo, illumination, tach, and temp, “somewhat” operational, I’ll be satisfied.

I’d much rather go to a Dakota Digital IC but can’t justify the $750 of mine works.


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[Jays85foureye]

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