Why would only the center brake light work and not the left or right brake lights on a 2001 Chevy Astro Van when the bulbs are good?

Answer 1

You have a bad: *Turn Signal Switch *Bad Fourway Flasher Brake lights for the left and right are wired through the turn signals, if your switch is bad (Open) on the turn signals in rest position, the brake lights will not work. The same is true for the emergency flashers. Diagnosing which one it is, as well as replacement, is very advanced for the average person. I suggest taking it to a reputable electrical shop. There is a recall on this problem. Contact your dealer. If not, get a new hazard switch and replace the old one on the steering column ($21.00 and about 5 minutes work). We used a matchstick slid in next to the hazard switch for a quick fix - have someone stand outside and tell you when the brakelights come on while you wedge stick in.