instrument panel lights

i have replaced all light switches, checked fuse, and put new bulbs in, but still have no instrument lights at all. the engine, seatbelt, airbag charge, oil lights all work, but the background lights do not. is there something i am overlooking? please help

the car is a 90 model ford taurus. it does not have the digital dash, and no tach. sorry about that!

Check the dimmer, I had the same problem with my 94 Taurus, and turn out to be the dimmer