I have a 1999 Silverado 1500 that has some serious issues and wanted to see if anyone could give me an idea of where to start:

Left blinker works only on occasion. When it is working everything else seems to be too.

When it is not working you hit the switch makes a noise but doesn't blink. When headlights are on brake lights stay on continuously until you hit the un-working blinker at which time they go out. Cruise will also work only when the left turn signal that isn't working is on.

Any help would be greatly appreciated.

 

Had same problem on my 1999 Silverado 1500 4x4. You need to replace the multi-functiom switch on the steering column. Not a hard job to do and prices on E-bay around $60 with shipping. They all come from China unless you buy from a Stealer than pay out your A--. Have had good luck so far on mine after 2 yrs. Their are U-tube videos on how to replace switch.