1987 Chevy Caprice right turn signal

Electrical problem
1987 Chevy Caprice V8 Two Wheel Drive Automatic

when the car is off and I put my foot on the brake the dash light comes on and 2 directional lights on the front cap come on,
then the left turn signal works perfect but the right one only flashes dim and rapid when the lights are off. When the head lights are on it doesnt work at all. On the dash with lights off the right turn signal flashes fast like the bulb is blown (but its not) and with the lights on it doesnt work at all.