the normal condition is NOT "high to low" - the tail lights are the dimmer of 2 lights, the brake is the brighter, when the blinker is on, the brake light is what blinks, the tail light just can't be seen because the brake/blink light is so bright
when the tail lights are on both sides should be the same brightness, when you hit the brakes, bith light should appear to get brighter as the 2nd element comes on, the blinker just interrupts the brake signal to whichever side is selected - anything else means you've got it wired wrong or are missing a ground
sounds to me like you've got the wires reversed, or both the tail and brake/turn wires both to the same terminal, or the brake/turn wire is hooked to the wrong side of the socket and the tail light wire just isn't hooked up
Bill
