Hi All -

Time to test the collective hive-mind, I'm out of ideas. This post may be a bit lengthy, but the only way to resolve electrical issues is to eliminate other possibilities....

This all began with a simple brake light failure, top bulb, right side. When I pulled the bulb it was black on the inside with a bad filament, so either voltage surge or vibrations, etc...I replaced it and it was fine, then a couple weeks later, same bulb out again. That's when the issues below started. The second time it failed, when I pulled the tail light housing to change the bulb again, the bulb was NOT burned out and I verified it worked by wiring directly to a battery.

I've checked the usual fuses under the driver side dash, #15 7.5A and #23 10A, both are fine.

There are two bulbs (stacked vertically) on each side that are dual-filament (taillight/brakelight). Top Bulbs are wired with Black (assuming ground), Red (taillight) and Yellow (brake light?). Bottom bulbs are wired Black (assuming ground) Red (taillight) and Green (brake light?). (assuming color coding from my testing, I do not have a wiring diagram)

All four taillights (dimmer of the two filaments) work (Parking/Auto/On and whether the engine is running or not).

On a perfect vehicle:

When using the brakes, and car is running, all four brake light filaments illuminate (and center brake light on top of back hatch). When car is not running, just the two bottom bulb (L and R) brake light filaments illuminate (and center brake light on top of back hatch)

On MY vehicle:

I have tested the bulbs, they are good. Wiring is good, but can't seem to get a proper voltage reading on the right hand side upper bulb (Yellow/Black. Red/Black tests fine).

My tail light tests:

With car off - All four tail lights work in any of the three switch positions (parking/auto/on) (auto-on verified in a dim garage)
With car running - same as above.
Tail lights seem to be fine.

Brake light tests:

With car off - Bottom left brake light illuminates, nothing on the right side.

With car running - BOTTOM brake light on the left side illuminate, TOP brake light on left does not. NO brake light on the bottom or top, right side.

The brake lights exhibit the same behavior whether the taillights are on or off.

Here's the kicker: The brake light filaments on the TOP two bulbs (L and R) are ALSO used for turn signals and four-way hazards. When I use either of these, (car on for directionals, car on and off for four-ways) the brake light filaments in all four bulbs WORK!

I hope my explanation makes some sense. I know just enough about electricity and wiring to be dangerous...

What should I be looking for? A bad brake light switch? Doubtful b/c SOME of the brake lights (well, one out of three) work. Perhaps the Yellow wire is for the turn signals and hazards? Red supplies both brake and taillight (doesn't seem plausible)? I'm stumped at this point....

Is there a relay for the brake lights somewhere that I can check? I may end up just taking it to the shop, but if I'm overlooking something simple, I'd like to know before pulling that trigger.

Does anyone have a link for the wiring diagram for the taillight/brakelights? I've been searching, but haven't found one yet.

If someone can help me find a solution, I'll buy you a six-pack of your favorite beverage

Thanks in advance,

Steve