I've done my homework here. I have no side brake lights, top one works. Hazards, turn signal lights all work. Everytime I replace the brake switch (4-times now), will work for a few days then stop working. However, when I push the brake pedal in further, lights WILL work. I see that there is a Recall from GM on this issue exactly. I followed the instructions to a tee, told me to replace the hazard light switch only, in which I have done. With no identifying #'s on the multifunction switch, evidently these are good.

Now, If I push the brake pedal down a bit to the point of lights not working, I can giggle the pedal, and the lights will light up. I think my problem is the linkage from the booster. The pushrod from the booster is pretty loose, and I don't see where it can be adjusted at all. No nut, no threads. I can also turn the push rod clockwise and counterclockwise very easily, but won't tighten. Just thinking outloud, if that push rod is loose, maybe it's loosing contact with the switch at a weird angle as I depress the brake pedal???? Any ideas out there? I'm at my witsend here need help.

 

I replaced my multifunction switch, which didn't work either. I finally found the problem though. The female connector that plugs into the brake switch was partially fried. I replaced this pigtail, and wala!, I have brake lights, ALL of them. Hope this helps someone.