Why not troubleshoot the system rather than throwing random fixes at it hoping to cure the problem by magic?

Is there power at the tail light terminal of the switch? Is there continuity between the terminal of the wire at the switch and the terminal at the lights? Are the lights properly grounded?

Like Tiny said,
Quote
Sounds like you have a broken wire or bad switch.
Find the problem and fix it. Patching in a new wire over an old problem causes nothing but more trouble.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.