I have had a on going problem with my tail lights in my 96 I30. I have put new bulbs in and when the headlights are off, The outside left one will work and the Right side will work but it is really dim. When the headlights are on ALL of the light's light up, but when I hit my brakes my outside lights light up normal and the one's on the trunk go out? I was told it could be a ground? I have no Idea. Any input would be great

 

have any light bulbs been changed recently? Things like this happen when a dual filament 1157 lamp gets replaced by a single filament 1156 lamp.