99 E320 (W210) Right Brake and Parking Light
 

The brake light and front parking light on the passenger side are not working. I suspect a fuse is blown so I looked in the fuse box under the hood and the fuse box under the rear seat to find the fuse but its not listed in either place. I checked every fuse and they all looked good.

Is there another location where a fuse that protects this circuit might be located?? It mentions a fuse box near the light switch but I looked under the dash on the driver's side and didn't see access to a fuse box. Is it behind the plastic panels?

Yes, and it's the one where the fuse probably is. At the very end of the dash (not on the front or under) on the left there is a panel. Note the drivers door must be open to see it. Pry off the panel to access most of the fuses associated with external lights.

Good luck.

My '96 W210 E320 had the same problem since new, which baffled the technicians, because the bulb and everything else seem ok, and they couldn't figure out what it was.

It turned out that the rear light module of the W210 had a common bad-contact problem. To this day (14 years later), the problem still comes back once in a while. But the fix is simple: just switching the light bulbs from one side to the other seems to help. It also helps if you clean the metallic area around the hole where the bulbs are inserted with sandpaper.