Ok, I give up on the search after reading thru 10 pages and 2 years worth. Only thing good I found is a link from geezer, but it's dead.

I'll be putting in a tic toc tach in place of the fuel guage in my 68, along with auto-meter console guages.

Buying all new repro wiring harnesses doesn't excite me much, but I do need some ideas from guy's who have done this, and perhaps sources for factory style terminals to add the the existing dash, inside fuse block, and engine harness so I can make up the wiring as nicely as possible. I've looked at the diagrams in the assembly manual, but they real hard to see, and don't really show a lot of detail. I do want ALL the warning lights to continue to work, as well as the new guages.

Thanks for your tips.

I did it using junkyard harnesses for donor parts. It's not hard, just time consuming making sure the connections are right. I spent a lot of time tracing the speedo/tach circuits by hand to confirm each function.

The seperate wiring diagram catalog is better than the AIM diagram. It's bigger and a bit clearer.

You will need the extra harness to tie in your console gauge package. Once you start running the wires it will make sense.

Thanks Carl. I won't have a problem running the wires, or even making up a connector for the console guages, what I'm really looking for is a vendor from whom I can buy the pins and stuff to add these wires to my factory harness. Since my wiring is in good shape, and I want to keep both the idiot lights (hmmm, is the GEN light in the tach? and I appear to have another RED light next to the turn indicator in the fuel guage, it doesn't ever light up, what's it for?) I'm not sure a new factory style harness would be the answer. A doner harness could supply the pins and wires tho. Anyone have one they don't want? No junkyards around here with anything close to this old.

Gen light is gone on gauge cars.

Low fuel light on LH side, and Brake light on RH, speedo. No lights on Tach except turn signal.

Any late 60-70's GM car can be used for harness parts.You may not get the same color wire that the manual states, but it will work.

If you have upgraded the charging wire to a larger gauge the amp meter will likely not work. There won't be enough voltage drop for the gauge to operate correctly. Another option is to use a voltage gauge. A small Autometer gauge with 13V at 12 o'clock can be easily adapted to the stock gauge face. The only thing that is off is that when the engine is off the gauge reads full left deflection. The stock needle can also be used.

Good luck.

Sorry about the dead link, my isp changed something and I had to change my web page to make it accessible. One person informed that netscape would give them an error but I tweaked the html again.
Let me know if you can access it or not. If not I’ll try to tweak it again. There are too many large documents to email so if you can’t pull it up, it would probably be easer for me to burn them to a cd and mail it to you.
http://www.gvtc.com/~rlaa/

I got em, Geezer, and thanks. Exactly what I was looking for.

Judging from Carls post, I got some homework to do. With my current setup, I have oil & temp lights in the speedo (left side) and Gen and Brake in the fuel guage.

There's NO lghts on the tach? As I understand it, if the gen light isn't connected the alternator won't work. I won't be using the oem console guages, and I bought a voltmeter, and I'd like to keep the idoit light working. And what the heck turns on the "low fuel" light? Think I'll go study those wiring diagrams.

The main thing is the pin connector diagram. With that you can figure where the wires are suppose to be. It’s been 20 years since I’ve done a conversion using those diagrams but I used them to install a 67 Camaro tach and console gauge set in a 68 firebird. I don’t think I ever got the low fuel light to work though. If you do a search for low fuel light, there was a pretty long thread about how they work. Oh yea. I’d definitely go with a voltmeter instead of an ammeter if I weren’t using factory gauges.

You will need the supplemental console wiring diagram. That will have the low-fuel module requied for the low-fuel lamp. It attaches to the back of the fuel gauge.

I don't know about the early models, but the later style CS alternators do require either the dash lamp or a 10 ohm resistor to excite them.

Nope, no lights in my tach. Oil and gen lights go away but can be added in somewhere else. There's a picture on my website of the speedo cluster.

With the a/m guages in the console, I'll have a volt meter, and an electric oil pressure. Since 2 out of 4 won't match up, I'll make up my own harness for these. Not a problem at all.

I'm not going to upgrade my charging system. Beleive it or not, whatever alternator is in it (and no, I'm not sure, but it is externally regulated) works fine. Even with halogen headlights and a 600 watt stereo, I've never had a problem keeping it charged. The battery that was in it when I bought it five years ago is still there, too.

It's my understanding that without the gen light, the regulator won't work and the battery won't charge. What takes the place of the light on a factory guage car? Or am I wrong on this?

I wish my memory were a little better. Ragtop #1, 20 years ago, I put in 5" a/m tach and speedo.... AHH, the brain cell awakes! THE CHARGING SYSTEM WOULD NOT FUNTION WITHOUT THE GEN LIGHT, AND I ENDED UP PUTTING IN AN INTERNALLY REGULATED ALTERNATOR... So back to my problem. Does anyone know what I'm talking about? Do I?

Stopped by D&R today and brought home a new tic toc tach. You guys are so right, no idiot lights on this thing at all. So now I have a speedo with an oil & temp light, and a gen & brake light with no where to go.

Suggestions?

ok, rolling on this now, but need to verify a few things. Got the dash apart, comparing my stock pcb with a pic of the one for the tach, and the tach itself. I am going to modify the existing pcb rather than spen $130 on a tach one.

Tach has 3 connections. From the back of the guage, the lower left looks like switched ignition power for the tach, will use existing wire that powers the idiot lights, with a modified connection in the circuit board.

Lower right is clock, need new wire to bat, through pcb.

Top wire is coil signal, and DOES NOT appear to connect thru the pcb? Is this right?

Then, the tach has a circuit bd on it, with a potentiometer. I assume I can adjust that to make it work right?

Finally, I don't seem to be finding a new lens that has the hole in it for the clock adj. knob. Do they exist somewhere, or do I have to drill the hole? If I hafta drill, andyone have a template?

On the factory gauge the tach signal is seperate from the pcb. If memory serves, it's a stud on the back of the tach that the signal attaches to.

The factory tach does not have a pot. If you are unsure try test wiring it up to your car and see what happens. Use a seperate gauge for calibration.

I drilled the lens on mine. You may be able to gauge the hole placement by the pic on my website.