74 Tailight Problems
Check main feed from battery under dash to amp gage, amp gage to splice. Unwrap splice and inspect its condition repair if necessary, and rewrap with 3M # 33 electrical tape not the cheap stuff. Continue inspection from splice to fuse block. From fuse block, and headlight switch follow each conductor looking for a chafed, burnt/melted, or cracked area. Somewhere between main feed splice and kick panel connection there is a fault to ground.