LEDs failed

Below is the high-mount LED brake light for my family's car Toyota Caldina

ST-215G. As you see the photo, two LEDs indicated by arrows are less

brighter than others. The name Caldina is not familiar to US people. The car

has been sold in Europe and in Oceania with a name of Avensis but it hasn't

been sold in US. In Japan and in Asia, it was named Caldina.

Although LEDs last much longer than regular bulbs, I have seen many

Caldina's high-mount LED brake lights failed. So the problem is not unique

to my family's car. The problem has started several years back and became

darker and darker as time went on. Now it has finally reached the level which

couldn't pass the Shaken or the inspection by the authority. In order to pass it,

I have needed to do something.

It was strange to me that Toyota has selected and used such poor quality

parts for this application. I knew they were very good at quality engineering

but this was one of the exceptions as far as I knew.

Those12 LEDs are all packed in a molded plastic housing and you can not

replace the failed LEDs without breaking the mold. So it is supposed to

replace the whole unit. But the parts shop nearby didn't have a stock. I was

in a hurry for the Shaken and I needed to fix it cutting the plastic housing and

replacing the failed LEDs.

I managed to succeed to cut it and install new LEDs which I had in my parts

box then sealed the housing using a HotMelt. I replaced 3 LEDs since the 3rd

one from the left was a bit darker. Those 3 new LEDs were not the same with

original LEDs but they were emitting as good as below and it actually passed

the Shaken. So without buying a new brake light unit, now it is working perfectly.

The current going through the failed LED was about 20mA and this was the

same with non failed LEDs. Also the Vf was the same. Only the emission

was much less. This can not be detected by the current monitoring warning

circuit. The other day, I dare stopped the function for the Celsior's similar

circuit after changing brake lights from bulbs to LEDs. Judging from the

symptom, it may be OK to do so. For the LEDs the failure detection should

be done by the actual strength of the emission not by the current only, I find.

The car Caldina ST215G is in use of so many imported parts from Europe.

For examples, the head light has mark of Magnet Marelli and the side marker

too. Some people say the car was mostly designed in Toyota Europe in

Belgian and manufactured in UK. I suspected that those LEDs were not

made in Japan but made in Europe. I used to have very hard time using

semiconductors made by European companies such as S??????, P?????

and I?? In 90s. They were quite improved later on but there were many

Japanese engineers who had very hard time. I'd say I am exactly one of them.

The negotiations with them was not easy but it was a good experience to me.

Below is the actual failed and removed LED. I wonder which company has

made this?