I just swapped my 86-92' style taillights out for the 85' style and changed my rear turn signals ,everything else works like the right turn sigs and hazzard but the left tun sig stays on and the rear turn sig light is out now ,when I first wired it ,it all worked great ,is it a possible shot bulb or just a bad harness?

 

yeah check your bulbs..a burnt bulb will cuase the signals not to blink on many GM cars. next thing is check your grounds, primarily the one on the left side under the tailight assembly or its in the well under the panel.