97 Diamante Radio Light Problems?

I would say that you have a problem with your wiring from the light switch to the stereo. In some cars they have a LED screen on the stereos because they don't have to have to have back lights. If the problem isn't a connection in the wire or something take the stereo out and check the back light circuit inside stereo. There might be a fuse for that circuit or it might be a burnt out bulb for the display. A person never knows until they take the time to check. If you don't know how to take the stereo out safely then take it to an auto sound retailer and see if they will take it out and repair it. If they don't do that it might be a good idea to get a new stereo. It also might be cheaper in the long run. Good luck.