I have a 68 Cutlass S that I am adding a new gauge to. I have removed the 'clock delete' bezel and installed a Classic Instruments, Quad Cluster (see picture below).
I have also included a picture of the back of my current 'idiot light' gauge and a picture of my schematic (using Dropbox).
I need some wisdom on wiring up the new gauge. Tell me where my thinking is flawed.

There are 6 terminals on this gauge.
1. Oil pressure signal. It appears the blue with white stripe wire is the one I want. I intend to snip this wire from the old gauge and connect it to the new. This blue wire runs thru the firewall to the new sending unit.
2. Labeled '12VDC switched' on new gauge. Need some advice where to tap in for this.
3. Fuel level signal. Going to wait on this one. Old fuel gauge is fine and may need a new sending unit to wire the new gauge. So nothing to do here.
4. Dash lights power. I believe this is the power for back lights on the gauge. What's the best choice for power here? Also, I'm concerned that the light on this new gauge may be way brighter than the older ones next to it. Any ideas of putting in some kind of in-line rheostat / resistor / dimmer so I could equal them all out?
5. Ground. Just plan to run a new ground wire to another ground under the dash.
6. Temperature signal. This appears to be the dark green one into the old gauge. (Schematic also shows a light green for Temp Cold Lamp, don't believe I have that). So, my intent is to snip the green from the old and connect it to the new. This wire runs thru the firewall to the new temperature sending unit.

Any advice would be really appreciated. I do not want to be under that dash any more than I have to!
Thx, Bob



https://www.dropbox.com/s/wk0srai1gn...39.24.jpg?dl=0

https://www.dropbox.com/s/fv9l0sfkx9...31.03.png?dl=0

 

I'll try to help a little. My experience is with 70 -72 years but your 68 pretty darn close. Simply check these with a volt meter.

#2 that pink wire is probably it. 12v on, no power off. Check it to be sure.

#4 the gray wires, these are probably powering the back lighting, with light switch on.

#6 I think you are on the right track there with green. As long as the sending unit is compatable with the new guage, I'm thinking that's it.

The orange wires in your second picture/diagram are probably hot all the time.

Again, a volt meter and some testing will all ways confirm, diagrams all ways nice too. Never seen that gauge set up, sounds cool for you 68 guys. Good luck.

 

2. Labeled '12VDC switched' on new gauge. Need some advice where to tap in for this.
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Diagram says the Pink wire feeds the lights so that would seem ideal for your new gages.


4. Dash lights power.
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I believe that a Gray wire [3rd from the top in the diagram] is the dimmable dash lighting.