Brake Light Problem --- Help!

[AlK]

Before I describe the problem, let me first say how much appreciate this technical forum. I am a recent convert to Porsche (2007 Boxster), having been a BMW guy for many years (2002, 320is, '88 M3 which I still own). But I don't like the current BMW styling and I think they have traded "road feel" for comfort. The Boxster is the most responsive car I have driven and it just feels as if it is an extension of the driver.

Here's the problem: yesterday the "service left brake light" message appeared on the display screen. I removed the left tail light assembly and tested the brake light bulb. It was fine, and lit up when I used a separate 12v power supply to test it. The brake light voltage, measured both at the harness plug and on the tail light bulb circuit board, measured only about a quarter volt. I checked the fuse, and of course it was fine. The right brake light operates as it should. It seems like the voltage is leaking to ground without causing a dead short, which would blow the fuse. Anyone have an idea what is going on?

[harryrcb]

Originally Posted by AlK

Here's the problem: yesterday the "service left brake light" message appeared on the display screen. I removed the left tail light assembly and tested the brake light bulb. It was fine, and lit up when I used a separate 12v power supply to test it. The brake light voltage, measured both at the harness plug and on the tail light bulb circuit board, measured only about a quarter volt. I checked the fuse, and of course it was fine. The right brake light operates as it should. It seems like the voltage is leaking to ground without causing a dead short, which would blow the fuse. Anyone have an idea what is going on?

The only thing I can think of is possibly a pinched wire, or somewhere in the trunk and I would suspect on the drivers side there is a connection point. The wire comes from you brake light switch (or power source) to the back and splits up , one going to the right brake light bulb, another going to the third brake light bulbsss, and the third going to the left bulb, it possible something is going on with that connection. try tracing the wire from your left tailamp (I think its black/orange) back to that connecting point and see what voltage you are getting there. Hope this helps

[Wayne 962]

Yes, it could be a pinched wire, or even could be a poor ground connection. Try testing the bulb connection to ground (resistance) and see what it is...

-Wayne

[AlK]

It was the #@!** bulb not seated all the way. Have to give it an extra twist.

[Wayne 962]

Originally Posted by AlK

It was the #@!** bulb not seated all the way. Have to give it an extra twist.

Ha! While I always kick myself when I find things like this, it is always a relief that the solution was cheap and painless.

-Wayne