turn signal/park lights

I'm hoping someone can help, my left turn signal and park light come on at the same time. The turn signal does not blink, just stays on. If the park light is on both bulbs also glow. If the turn signal and park light are turned on at the same time, both bulbs go out. there is obviously a short somewhere.....I have had all the switches apart and cleaned them, this has not made a difference and have checked all the connections and all seem fine. please help.