So I have a dash board fault message - brake light fail and RH tail light out and then LH tail light out

The rear LED light flicker - the right hand one more then the left and the RH one sometimes goes out.

have read quite a bit about this problem today and have come to the conclusion that its eighter water / fault in the tail light units OR a faulty rear SAM unit. Its has been exceptionally wet here.

I have taken one of the tail light units off the car and it looks OK and whilst not absolutely dry its not wet. Tomorrow morning the other one comes off for the same treatment.

From my limited experiece its looks just like a poor connection BUT where??

Any further suggestions please.

Also where is the rear SAM unit located.

Is it a good idea to get it connected to a Star unit for diagnosis ?

 

Just sayin' Put in the original bulbs if eveything works trash the leds they are nothing but a pain and not necessary.

 

Errr..............no the LED's are OEM fitment........yes way back in 2006

 

The rear sam is under the fuse block in the box behind the seat.

 

If doing any fault finding here, don't rig up a 12 Volt PS - the LEDs run off 2.5 Volts.

 

I have not made any serious progress during this holiday period but I have been thinking about the issue.

The thought in my head is that this is still an earth / grounding issue.

In the image above the one illuminated block at low level is, I am pretty sure the end LED on the strip of LED circuit boards that make up the whole of the bottom area of the light.

I would have thought that the earth connection on each of the circuit boards would have been common (they are all daisy chained with ribbon cable) there isn't enough width of ribbon cable to earth each board I dont think.

So the query in my head at the moment is why are these two LEDS illuminated and the rest not ??

Anyone shed any light (sorry) on this ? Could it still be a supply issue ?

 

These are the daisy chained circuit boards I am thinking of - it seems that the very end one (furthest away from the connector) is working properly

There must be some logic here ??

 

The wiring for the led strip is more complicated than it looks, as has four wires to feed the segments.

Also bear in mind the USA specification has an extra function and has a side marker lamp in the same LED strip, which has an independent supply from the SAM.

So I think the four wires will be Ground, rear tail lights, Brake lights and side marker light (USA specification).

It is possible the LED's you see are the independent side markers.

A good diagnostic, like STAR SDS will enable you to monitor the switch status, and the output status to the lights, as well as force activation of each light.

You need to check the output of the SAM with a voltmeter, but as the SAM detects a faulty bulb or LED circuit, it turns off the output to it (Catch 22) and turns ON an emergency bulb instead !

STAR SDS has a guided fault finding to bypass this issue, which involves putting a large 70 ohm resistor across the SAM output and ground, to simulate a bulb. You can then fault find as normal.

Note just checked in STAR SDS and this is not a valid test for the LED Strip....!! only for bulb lights. Only tests are to check wiring is OK, and internal resistance of SAM, with ignition OFF is greater than 30K ohms and there is a small, less than 1V voltage at the light all the time.

SAM's do go faults, but so does the LED strips.

 

Should have added this

 

I think I may have found the issue - I unplugged the connector to the LED circuit board and found this:


Is that burning damage do you think or corrosion?


There are no failed components on the individual boards.

Is this the problem do you think ?

Is it possible to buy the circuit boards on their own ?

Thanks

 

Looks like a burn to me, as far as one can judge from a photo. You should be able to see/feel if the plastic has been scorched or if you can wipe of dried up dirt.

 

I am getting a Brake Light, (R) error code on my dash. All other lights on the right side operate and they appear to share a common grounding strip. The LED lights function with a remote voltage applied. The other two brake lights are illuminated when the car is running. I have cleaned with sandpaper the connection to the LED strip. It did not appear corroded initially. This is my first post.

 

Well welcome to the club! - so far I have not managed to rectify the same issue. I have been advised by a MB independent to carefully lever the contact pins down as they may not any longer be making good contact with the board.

I will try this in the next day or so

 

When I had this happen to me, it was a SAM issue.

Happened on my 2003 SL500 and 2002 S500