1988 Dodge Truck Turn Signal Does Not Blink

I have a 1988 Dodge D100 pickup, when I put on the left turn blinker the light comes on, however, it does not blink. Right turn signal works fine. At night when I have lights on, if I turn left blinker on the light goes out, also if I step on the brake with lights on the driver side tail light goes out. I changed the bulbs but still same. Help.