Tail light wiring question

[FL71C10]

I replaced the left rear taillight assembly on my 68 c10 because the plug was really bad and the lens was bad, so it was cheaper to replace the whole assembly.

The truck has a bunch of nasty wiring from trailer lights, but all of the rear lights worked except the backup lights (next project). I resoldered the wires back together, and my flashers work but the brake lights dont. Would that be the same wire?

Any suggestions would be appreciated.

Thanks!