Hi,

I'm confused about something with my 2002 Legacy L station wagon. The brake light and tail light are combined into a single bulb. When the car is running the tail light is out on the passenger side (all the other lights work fine). When the brake pedal is depressed, however, the brake light works. The bulb seems to be fine (since the brake light works) but something is wrong since the tail light isn't working. I don't understand how the brake/tail light combination works.

 

Any tips on where I should be looking to id the problem with the tail light?

It's common for one filament of a dual-filament lamp bulb to burn out.

Usually this is one of two issues:

 

1) Burned out filiment in the bulb

2) Corrosion in the socket.

 

Remove the bulb and replace it. It's the most likely culprit. If the new ones still is a problem, there is most likely a socket issue. Doubtful in the wiring. Both sides would be out if it were a fuse.