turn signal problems

[BCOWANWHEELS]

ok i,ve got a problem with my turn signals and front marker light-bumper park light. heres the symptoms, when park-headlights are off i have good working turn signals all around but when i turn on my park lights or head lights i dont have any left front fender marker-turn signal or no front bumper turnsignal and the left rear wont blink also. plus when park lights or headlights are on my left turn signal light on my dash board is on bright but dont blink. right side works perfect if lights are on or off. any tips to trouble shoot this circuit. could a bad headlight switch make this happen ?
bob