I have a 86 brat, the volt meter, gas guage, oil pressure, work and don't work, same with the tach, but that is working now. Also the 4wd light on the panel does not light up. Any ideas where to check? The gas gauge goes to full , then drops to about 1/2 when tank is full. The volt meter reads 8 to 9 volts , when the battery is at 12. oil pressure is all over the place.

Check the grounds in the engine compartement. Also may need to remove the dash panel to clean the grounds on the back of it. Check plugs that go into the back of panel also.