Just purchased an '83 300D Turbo. The dash lights for the speedo/tach are very dim. The adjustment knob will vary the intensity but from nothing to very dim. By very dim I mean just barely illuminated. Is this likely to be bulbs or the adjustment pot or something else?

Also there is no illumination for the switches (sunroof, rear defroster, antenna) above the climate control row with the headlights on. Is this normal?