Zig Zag brake lights when headlights on

[Slowcars4life]

1993 240sx. I am having a problem with the rear driver side brake light getting dim when I turn on the headlights. The other side stays bright and I have already tried replacing the bulb. I beleive it has something to do with the previous owner connecting the headlights together because the one was not working. I would like to fix this problem also, but I did not see any relays anywhere and could not locate a Haynes manual at my local auto parts store. Any ideas?

Thanks for the help

[JeromeS13]

Check all of the contacts within the tail light assembly. Clean them with steel wool.

[Slowcars4life]

All of the contacts have been cleaned previously. This problem only occurs when the headlights are turned on and I hit the brake pedal. It will not happen if the headlights are off. Can anyone tell me where the relays are? I heard they are located under the airbox, but is the box only visable when the airbox is removed?