1993 z71 k1500 and when you turn the left blinker on only one bulb blinks In the front. When I turn the right blinker on all four of them blink( two in each blinker. The other problem is when I turn on the headlights with left blinker, all the lights stay on and don't blink( the flasher does make a sound). When I turn the right one on with headlights, it stays on (no flasher noise). The problems I do know with the truck that could be causing the issue is 1. The left blinker light on the dash is broke 2. When I turn on the headlights the blinker light stays on.

 

1st, when did the problem start? And 2nd, it may be helpful to look at a wiring diagram, to see if something failed and connected the circuits in a funny way.

 

By any chance di you switch to LED's in the truck?