[VetteVet]

The power for your turn signals starts at the key switch with the 12 gauge brown accessory wire which runs to the fuse panel and powers the heater, wiper. and the turn signal flasher. I would start at the flasher by swapping the hazard flasher with it. If the hazards work then the flasher is good and I would proceed to the steering column connector. Unplug it and check the purple wire in the center of the harness side for 12 volts with the key on. assuming you have a volt meter.

If you get 12 volts there then the turn signal switch is probably bad.

The wires are good because the hazards work and the turn signal indicator lights don't work because they are wired into the turn signal light wires, which don't work.