I am the proud owner of 77 Classic and my left signal just stopped working. I checked all the wires and conections. What could be the problem? The light on the dash comes on but does'nt blink on and off like the right signal does.
Does the right signal flash or stay steady? If the right side stays steady also it might be the flasher unit that went bad. Ive had that happen to me in my dads 1990 buick century. Just food for thought.
If you test the bulbs and they are good, you might have a cut or broken wire for the left side directional lights. Like someone else said, you might have a bad ground, bulb out, or even a corroded light socket which could be the culprit. Hope you find the problem.
I'm not that familiar with a 77, but if the side marker lights are part of the signaling system check the bulb and socket there too. Don't assume that just because a bulb filament looks intact that the bulb is still good, either test it with a continuity tester, or connect it to a battery. My bet, it's a bulb, or corrosion in a socket.