For some reason everything on my instrument panel works except the gauge lights. Gauges themselves - good, turn signals - good, break notification light - good, heater and wiper controls - good. The head lights work too so I dont' think it's the switch. I replaced all the bulbs and fuses to o avail. Even checked the gorund.
The only thing left was to undo the harness tape and see what went where. Below is a diagram of what I found. Only what I thought as relative to the problem is depicted. There are of course many other wires, most connected some not but everything other than the gauge lights are working.

I hope someone can help.

Blue/Orange = gauge lights
Yellow/Black = ???
Black = ???
All conecters are female

 

I assume you checked the fuses as well.
Even though the headlights work it still may be the headlamp switch.
There's a coiled dial in the headlamp switch that works the instrument lights. Sometimes that dial gets a little loose or offcentered not allowing contact to be made.
I'd pop out the headlamp switch first since it's not that hard to do.
First disconnect the battery. Then pull the switch out like your turning on the headlights. Next feel under the dash to the headlamp switch. There will be a little button towards the back on the side that you push in that allows you to pull the **** the rest of the way out.
You can then take a large phillips head screwdrivers and unscrew the headlamp switch (where the **** was) and drop it out.
The connection may just be corroded as well.
It's more than likely the switch.

Erick

 

Yeah, fuse is good. I checked the connections in the switch like you said and they seemed fine. Probably are since a brand new switch I bought today didn't change anything.

 

May be the voltage regulator. There's one on the back of my 66 dash - I assume a 67 has one as well.

 

The gauge lights are out on my '68 as well. I've also replaced the voltage regulator, bulbs, and headlight switch. I'm still trying to track it down.