Bizarre 3rd brake light failure.


2112

Blue/white 06'
Mark II Lifetime
I happen to notice that my 3rd brake light was not coming on when I pressed the pedal.

I decided to bench test after removal using a car 12volt car battery. When contacting the terminals, it will sometimes illuminate, at which point making several other attempts will give illumination anywhere from 4 to 7 times.

Then nothing. No matter how many times or ways I contact the terminals, I cannot get it to function.

After letting it sit for a while, it will fire back up, 4 to 7 times then nothing again.

When it’s on, it is bright and all bulbs appear to be working fine.

What is going on? Are these LED? Is this how they fail?

BTW, these are not serviceable units as they come from the manufacturer.
 
Last edited:

Art138

GT Owner
Mark II Lifetime
Jan 4, 2011
629
Weston,FL
I happen to notice that my 3rd brake light was not coming on when I pressed the pedal.

I decided to bench test after removal using a car 12volt car battery. When contacting the terminals, it will sometimes illuminate, at which point making several other attempts will give illumination anywhere from 4 to 7 times.

Then nothing. No matter how many times or ways I contact the terminals, I cannot get it to function.

After letting it sit for a while, it will fire back up, 4 to 7 times then nothing again.

When it’s on, it is bright and all bulbs appear to be working fine.

What is going on? Are these LED? Is this how they fail?

BTW, these are not serviceable units as they come from the manufacturer.
There are a few on eBay-one with best offer in case you can’t get yours to work.
 

fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,495
Belleville, IL
Is this a totally stock car that only you have owned? A long time ago Black Ice invented a small electronic board that was easy to fabricate and install. It would make the third brake light pulse when you applied the brake pedal to make the car more noticeable when stopping. This was a very long time ago. I don't think anyone knows how many were made or installed. This is an outside long shot, just FYI
 
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2112

Blue/white 06'
Mark II Lifetime
Yes, stock. I have a pulsing unit I hoped to install, now I’m rethinking it.
 

Submoose

GT Owner
Mark IV Lifetime
Oct 28, 2023
66
St. Louis, MO
I’m no engineer but this sounds like the kind of response that is due to heat. There may be a broken connection that is so small it functions until resistance causes something to swell/move which breaks the connection. Now, that and the price you paid for my guessing is nearly useless but I’ve been confounded by broken connections many times and felt worth mentioning/
 
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2112

Blue/white 06'
Mark II Lifetime
maybe you are right and it's heat. It always seems to work when it's had time to cool,, just shocked that if it's heat, it builds up quickly and causes the unit to not illuminate

I will try getting the unit rebuilt before tossing it.
 

PeteK

GT Owner
Mark II Lifetime
Apr 18, 2014
2,285
Kalama, Free part of WA State
Now that you have mentioned it, I better go out and check mine too.
 
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