I have a 2006 LR3. I thought the left top brake light was burned out so I purchased a new bulb from the dealer. There are two filiments in the bulb. One of them burns at the proper intensity when the lights are on. Yet, when I press the brake, this filiment goes out and the brighter brake filament does not light up. The bulb can only be inserted one way so I know that is not the problem. Any ideas????

 

Swap bulbs from the other side and see if it does the same thing.

 

Thanks for the suggestion. I swapped the left and right bulbs but continue to have the same result.

To clarify my initial question, recall that each bulb has two elements, a dim element and a bright element. When the headlights are NOT on and I press the brake pedal, the dim element illuminates on the left side but on the right side, the bright element illumimates as it should. When the headlights are on, the dim elements on both sides are illuminated as they should be. However, when I then press the brake pedal, the left side dim element goes out but the bright element does not illuminate as it should.

 

So you swapped bulbs and the know working bulb does the exact same thing?
And the "bad" bulb started working normal?

 

Yes, so that tells me that both bulbs are good. When they are on the right side of the vehicle, they both perform properly. When they are on the left side, they both show the same problem.

 

Then it is a wiring problem, start with the bulb holder, can you switch the bulb holders from side to side?
Start simple and work your way from there.

 

I know this is a bit old, but did you ever figure out the problem. Im having the same sort of issue on my 05 lr3.

 

It is a bad ground. It can carry enough current for the "tail lamp", but when you use the brighter brake lamp, the circuit can't carry the current and it goes open. Either a bad socket or bad ground.