Faint rear brake lights / turn signals

[low79fx]

I did the same to me tail lights. I soldered a separate wire to the lamp socket and attached to frame when routing new wires. The problem with the original design is that ground is depending on the very minimal surface contact that the screw that holds your rear taillight housing provides. Which amounts to only the thickness of the sheet metal touching the thread, getting a little air, dirt or moisture in there and you will sure lose your ground source or create a lot of resistance for ground to complete. Thus causing your dim light problem. Yes try soldering a wire to lamp socket for a good ground as others have recommended.