61 valiant turn signals ??

Furyfrank, here's another thing you should do: back the car up to a wall or window so you can see the stop light reflection from the driver's seat. Switch the ignition off. Step on the brake. See the stop light reflection? Keep your foot on the brake and your eye on that reflection as you move the turn signal lever into the left-turn position. HOLY FLAMING SNOTBALLS, where did the stop light go?!! It switched off because your turn signal switch broke the stop light circuit to the left lamp and completed the turn signal circuit to that same lamp. But the ignition is switched off, so there's no power to the turn signal flasher, so no power to the lamp. Now move the turn signal lever back to the home/no-turn position and see how the stop light comes back on.

If that doesn't help you understand that yes, there is such a thing as a turn signal switch failure that causes the problem you're having, well… ¯\_(ツ)_/¯