T he radio light keeps going from bright to very dim

Are you headlights on auto(if equipped)? If so and this is happening when your headlights might be coming on and off try adjusting your dimmer switch to a higher setting. Some vehicles Radios have a normal(bright) setting for day time( or anytime headlights are off) and the radio lighting is controlled by the dimmer switch when the headlights are on. Hope this helps.