1997 E36 Brake light circuit failure

[Seeker <rfg@xxxxxxx>]

>>Date: Sat, 21 Apr 2001 09:13:19 -0400 From: "Stephen E. Clark"
>><sclark46@domain.elided> Subject: 1997 E36 Brake light circuit failure
>>
>>Help,
>>
>>I was getting this message intermittently, even though the brake lights were
>>working. Now I am getting it continuously even though the brake lights are
>>working. I have cleaned the bulb bases and sockets and the all the places that
>>make contact. What now?
>>
>>Any suggestions would be appreciated.
>>
>>TIA, Steve

Steve - 

    Below, one after the other, is info I have copied from the Digest re
this problem.

    1. 
That was very helpful. As a matter of fact that's exactly what my problem
was. I took a flashlight and looked in the socket and found a burnt section
on the plastic part of the brake light assy where the metal strip is
supposed to make contact with the bulb housing. This caused the contact to
not line up properly with the contacts on the bulb housing. I pried the
contacts out a little bit paying close attention not to break it (they are
very easy to break if you bend it too much). Put the bulb in it's housing
back in the brake light assy and it worked like a charm. Don't know if I'm
going to have to replace the whole brake light assy in the future but this
seems to be a good fix.

Does anyone know what causes the plastic to burn like that in that
particular location? does the bulb (looks more like the metal contacts that
did it) get that hot to melt the plastic?

    2.  
Answer:  I have/had the same problem in my E36 ('97 328ic) where the OBC
would read "1 brake light fail"  After several bulb replacements, by the
dealer on many occasions, the problem was still there.  Then I decided to
look at the taillight assembly in daylight and noticed that the place where
the bulb screws on to had "partially burned off" and hence was causing the
OBC to trigger with a message.  I read about the area where the bulb snaps
on being burned over time on some other message board.

    In any event, this weekend I went to my local BMW dealer and told the
service rep my problem and what I thought the reason for the problem.  He
agreed that a part of the assembly was burned from the heat generated and
offered two alternatives. 1) replacing the left corner taillight assembly 2)
turning the bulb enough so that it has contact but not so much that it is
not making contact.  I opted for fix #2 and said that I would drive this way
until the OBC message came on again.  I am sure that I have to replace the
entire assembly some time in the near future.  It is quite disturbing that
BMW has a bulletin out on this problem but won't recall the lights and will
only replace them with cars having under 50K.  How generous of them!!

    3.
I too was plagued by the mystery "Brake Light Circuit" message on my
OBC.  I would check my lights and they were working properly.  By
turning the car on and off the message would reset and then a few days
later it would come up again.
I recently went to the dealer for a few minor things and mentioned to
the mechanic that I was getting false check messages out of the OBC.  He
solved the problem and gave me an insight into what the cause.  The OBC
does a continuity (resistance) check through the bulb and will pop up a
message if the resistance is not in spec.  For this reason he warned me
to use only BMW bulbs because they fall within the OBC expected range,
whereas what you find at the typical auto parts store may or may not.
He popped out a bulb, scraped off the housing contact and the bulb
contact with the tip of a small screw driver.
The system must be very sensitive to minor resistance changes because by
removing the minor layer of oxidation on the contacts the problem went
away and I have not had an OBC check message since.  I followed up on
the mechanics advice and bought a couple of BMW bulbs from the parts
counter so that when they eventually blow I can avoid false warnings.
Try cleaning your contacts, if this doesn't help, try new BMW bulbs.

4.
This is a known (and documented I believe) issue with E36s. It's a faulty
brake light switch. That what causes the intermittent problems. Replace the
part (sub $30 I believe) and should find things will be back to normal.

Hope some of this is useful.

Seeker

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