I have a 1989 240 sedan and the passenger side brake light is giving me trouble. Any help would be greatly appreciated!

The bulb works when the headlights are on, but will not work as a brake light. The rest of the housing unit lights up fine, as does the left housing unit (brake light included). I've tried the basics thus far, including changing the bulb, bulb casing, and light housing circuit pannel. No difference noted with the new circuit pannel. I lubricated the connectors as well, and this didn't work either. The fuse looks good with no corrosion or break.

Am I looking at a switch here, or perhaps a wiring issue? Thus far I am stuck, and since I have little electrical experience, a few pointers would greatly help.

Just to clairify a bit. The right sided dual filiment bulb works fine as an indicator that my headlights are on, but that's it! As a brake light, it does't work if the head lights are on or off. If the headlights are off, the bulb remains unlit with pressure applied to the brake pedal. If the headlights are on, the bulb is on, but won't get any brighter with pressure applied to the brake pedal.

I'm planning to check the grounds, install 2 new identical bulbs, and then use a test light from the Bulb Failure Sensor.

Could also be a bad Printed Curcuit Board.

I had a similar problem on a 90 sedan, and it was the printed circuit board for the light. Its been a while back, but I remember being able to wire around the board and make the light work properly.