dash board lights
The panel is grounded through the mounting screws. If you take it out for maintenace, there are a few things you should do. One, is to add a pigtail ground wire which then bolts to the dash frame or column support.
Other problems......
Loose harness connector pins at the PC board which can be repaired
Sometimes the gauge VR "socket" spring clips lose connection to the pc board traces. You must solder jumpers across
The stud nuts for the gauges loosen / corrode, you need to loosen/ tighten them to scrub them clean and tighten, good idea to replace with "real" nuts.
And......of course clean, inspect the lamp sockets and replace the lamps. Some on here have gone to LED with various results
Here's a good thread on PC board repairs
Printed circuit pins repair