Dash lights on 66 won't work. Tried replacing switch no difference. They had flickered when first bought. Any suggestions? Location of ground? Maybe wiring diagram would be helpful. Could trace.
Before I get crazy and take it out. Don't need to see how fast I'm going anyways do I? Not an excuse to get out of a ticket.......

 

Most likely your problem is the ground wire on the instrument cluster, there are a couple, you'll have to loosen up the steering column & pull the cluster back to check behind it for the ground wires. Another thought that comes to mind is to check the ground at the front of the light harness under the hood, make sure all of the ground wires are cleaned & making good contact. One of the other members has posted a schematic here on the forum, if you do a search, it is easy to find & it will certainly be helpful.
Don

 

It takes two fuses for the dash lights to work. The voltage comes through the tail light fuse first and then through the rheostat, and then through the instr fuse. If you have tail lights, that fuse is good. Measure, don't just look, the fuses can separate under the cap instead of melting. If both those are good, you probably have a bad rheostat in the headlight switch. Measure for 12v on the dark green wire coming out of the headlight switch connector. If don't have it there the rheostat is open and you'll need a new headlight switch. If you do have it there, then you can worry about an open wire or bad ground on the instrument panel. I doubt you have a bad ground, other things are grounded by that, and the bulbs ground via the clip that holds them in the hole.

First step, measure fuses mentioned, the second and third fuses from the bottom. You should have 12v on both sides of both those fuses. If you don't post back where you do and don't have voltage and I can better tell you where the problem may be.
PS the dark green wire from the rheostat I mentioned ties to the left side of the instr fuse, so you can measure it there instead of at the rheostat.
If it looks like the rheostat is bad, post back and I'll tell you how you can bypass it. The dash lights will no longer dim, but they'll work.

The fact that they flickered before and don't work now sounds like the rheostat is bad.

 

Great info. I'll try it! Thanks

 

If your turn signal and high beam indicators work, it is probably not the ground. It is easy enough to run a jumper wire from a known good ground to the instrument panel if you think that might be the problem.