backlit instrument panel
 

When selecting the lights for night driving, all of the instrument cluster is backlit except for the Tach. Any clues? All the fuzes are OK.

sounds as if the tach illuminating bulb has burned out. There are different bulbs in the instrument cluster.

Instrument bulbs:
12v 3w: 999-631-304-90 / analog gauges
12v 1.5w: 999-631-303-90 / digital display (3)
12v 1.2w: 999-631-302-90 / idiot lights