Instrument Cluster Lights Not Working

Have you checked for voltage getting to the cluster?

You're making this WAY too complicated. Check for voltage on the orange wire in the black round connector. That should be the fourth terminal from the keyway.

Do you have the original radio or an aftermarket replacement? If it's the original one, you should notice the display doesn't adjust with the headlight switch rheostat, and there's no back-lighting in the faceplate either. Suspect the head light switch.

If you have an aftermarket radio that was recently installed, they likely used the lighting wire for a ground wire. In that case the 5 amp fuse will be blown.

Previous owner might have blown the fuse for the lights. There is no ground wire in the original two radio plugs. You have to use that braided ground strap or black clip-on wire for the ground. There is a tail light wire to the radio to tell the display to dim when you turn on the lights, and there's a dash light wire to the radio to tell the display how much to dim. Because of the large number of bulbs on each circuit, both wires will read very low resistance to ground, and that's why people often mistake them for ground wires.

First check the 4 amp fuse, # 5, (not a 5 amp fuse like I mentioned earlier). If it's okay, check for voltage on both terminals when the head light switch is on. If there's no voltage there, go back to the head light switch and measure there.

The head light switch isn't too hard to remove to test voltages. Measure on the 18 gauge tan wire with the switch turned on. It's the one sitting kitty wumpus in the corner. If there's nothing there, check on the 18 gauge black / yellow right next to it, (half way between the front and back of the connector.

Also look at those two terminals in the connector to see if they're blackened from being overheated. By this time you should have found the problem because that last voltage is tied to the tail lights which I assume are working.