I think I figured out how the blinkers work. The parking lights have three wires, black (ground), blue (blinker power), brown (headlight switch power). The side markers have two wires, brown (headlight switch power), blue (blinker power).
When the blinkers are activated without the headlight switch on.....there's power to the blue wire an no power to the brown wire. The side markers get ground from the brown wire. The flasher interrupts the power by alternating ground/unground (I think this is right).
When the headlights come on, the side markers get power from the brown wire and use the blue wire as ground. When the blinkers are activated, the side markers have power to the blue wire and power to the brown wire. When that condition is present, the flasher is activated and interrupts power to the blue wire and grounds that. The side markers go on and off with the flasher.
Now the parking lights, when the headlight switch is off, the side markers and parking lights blink together. The parking lights use the black wire for ground, while the side markers are grounded via the brown wire.
When the headlight switch is activated, the brown wire is powered. This turns on the parking lights. Since the parking lights get ground from the black wire, when the blue wire is powered by the flasher, the parking light blinks. When the parking light blinks, the side markers are in the off sequence. This is because when the blue wire is powered with the headlights on, the side markers lose ground
Whew! It took me a couple of hours to figure this out....but it's really quite simple.
Let me know if I'm totally wrong about this.