I had a similar problem. It turned out that a former owner bent the metal frame of the dash where the instrument panel plugs into the dash.
The grounds for the instrument pannel were not making contact with the body... thus the instrument lights kept going out.
Solution: Take a pair of waterpump pliers and streighten out the bent metal of the dash.
1993 190E 2.3
2000 Toyota 4x4 Tundra