Blinker only works when headlights off

[bennylava]

Hi all. I'm having some trouble with my blinker, which is preventing me from getting the required state inspection sticker. For some reason, my driver's side blinker will only work if the headlights are off. If I turn them on, that side won't blink.

When the headlights are on, I'm also getting the "check your blinker" signal. Meaning that the green blinker indicator in the cab stays lit up at all times. instead of just flashing when the blinker is turned on.

The truck sat in my driveway for 4 months, and before that everything was fine. Anyone ever had this problem? It's an 87 silverado 5.7L 700R4 if that helps any. Thanks!