1974 c10 turn flasher

[Dead Parrot]

Do you get the same no-op result with the hazard flashers?

As a test, use a wire to jump the fuse box hazard terminals. All your turn/brake bulbs should light up when you activate the hazard switch.

Same for turn signal bulbs.

Of course, with no flash unit, the bulbs should be on full time.

Looks like a lot of corrosion in that fuse panel. Pull the fuses, clean the contacts and reinstall the fuses. Might be that simple.