in my 83 caddy radio the led only lights up on the bottom half how do i fix it:shakehead

good lord, if that's the OEM radio then it has lived a long life. It probably has some burned out lights/leds or loose wiriring inside. You would have to take it apart and see.

Definitely bulbs in a 80's era factory radio.

Replacing them is another story depending on how the radio is put together. My experience is with the Chrysler radios and their faceplate is held with 2 screws and clipped to the radio chassis (locking plastic tabs on the faceplate sides), removing the plate exposed the bulbs and some were actually servicable with bulbs from an auto parts store, just had to remove the colored covers and put them on the new bulbs and replace. I can't speak for the GM units but if your adventurous and want check it out you may be able to replace them just by doing the same.

No guarantees though, may be time to give the caddy some new sounds.