Left turn signal better than right

My left turn signal always works better than the right. Even at stop idle my left signal keeps flashing. My right signal stops flashing at idle. Both work at highway speed for lane change and full turn action. The alternator is new (100Amp). I always drive with my headlights on. I get a negative Ammeter reading at idle at stop, but engine is idling fine. Wiring harness was completely checked with recent restoration. Voltage regulator does not look OE.

1973 Duster, 225 slant, a/c,

Where should I look first?

Turn signal switch?
System voltage?
Ground?