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Thread: DIY: E32 Brake Light Circuit Warning Light Repair

  1. #1
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    DIY: E32 Brake Light Circuit Warning Light Repair

    E32 BRAKE LIGHT CIRCUIT -CHECK CONTROL FAULT MESSAGE REPAIR - By Master E32FAN

    "My 1992 735 iL had intermittent troubles with BRAKE LIGHT CIRCUIT. It persisted with three different CCM modules. So, it's time to replace the Brake Light Switch, right? Well, maybe not!"
    The complete story for a free repair on the shogun website, click fixes>>brakes>>> Check control fault message repair
    http://twrite.org/shogunnew/topmenu.html

    In case it is not working on IE11, use google chrome for the time being, working on that problem now to solve it.
    Last edited by shogun; 11-07-2014 at 10:06 PM.
    Shogun tricks and tips for the E32 series are HERE!

  2. #2
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    My thanks to shogun for hosting this repair note.

    It is a sweet, FREE, answer to the thorny BRAKE LIGHT CIRCUIT problem!

    The pdf is here: twrite.org/shogunnew/files/E32_BRAKE_LIGHT_CIRCUIT_REPAIR.pdf

  3. #3
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    That is the easiest solution, if it works. If not, you have to clean the switch http://www.nmia.com/~dgnrg/page_25.htm
    Some comments from a German forum (google translated) :
    The published solution is very elegant. The switch does meanwhile cost abt. EURO 40. It can be explained as imagined by a fireplace. The fireplace has a lot of soot on the walls of the fireplace. The solution - burn more wood or hardwood - the temperature rises and the soot is burnt too. The procedure with the switch is apparently similar. The burnt area shifts outwards and the contact is clean again.

    Contacts need some current load , so that the growing oxide burns . It is a self-cleaning effect, which just does not work with too low load. It is a small spark at the contact, brushing away the 'dirt' ...
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
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    Error messages "1 BRAKE LIGHT FAIL" and "BRAKE LIGHTS FAILURE" indicate lamp failures. In case you have a message "BRAKE LIGHT CIRCUIT", usually points at a brake light switch that's on the way out...
    and then you can try this trick.
    Shogun tricks and tips for the E32 series are HERE!

  5. #5
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    Isn't it easier to use electronic contact cleaner?

  6. #6
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    No, because it is not that comfortable to get the switch out above the pedal.
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    Thirty years ago, I was happy to slide on my back into the footwell of my car to perform a repair. Now, not so much.

    Today, I'd rather lean over the front power distribution box and do the work there.

  8. #8
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    Do you know offhand if this works on all E32s (including M60 cars)? (Before I check the wiring diagram, thought you may know...)

  9. #9
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    Quote Originally Posted by kansei View Post
    Do you know offhand if this works on all E32s (including M60 cars)? (Before I check the wiring diagram, thought you may know...)
    Yes it will work with 1993/94 740iA. See pg 6200-13 in the 1993 ETM.

  10. #10
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    Feedback from Dean from Australia:
    did the brake circuit high current clean burn fix again over the weekend and this time I'm hopeful it will fix it properly without having to remove the switch for a manual internal clean of the contacts. The first time I did it exactly as per the instructions and it did make a difference in testing. The warning error would come up on the dash CC display, but with nowhere near as much regularity as before. In a couple of weeks, I got the warning message only twice as opposed to almost every time I got in the car before.

    This time I pressed the brake pedal full stroke 20 times and let the test light illuminate longer each time to hopefully burn off a bit more of the carbon from the contacts.
    Shogun tricks and tips for the E32 series are HERE!

  11. #11
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    Additional info
    CCM pinout in detail, on E32/E34 pin 7 is brake light test, connection brake light test switch http://www.bimmerboard.com/forums/posts/275437
    Shogun tricks and tips for the E32 series are HERE!

  12. #12
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    Guys..If I want to "Try" just buying a new switch for a 740, what is the part number? (EDIT) The dealer says it's 8356527 and 165.00. Wow. ECS has for 132..I can't for the life of me find it on RealOEM and they appear to not be the same as a 735 or 750, which is very strange. What am I missing?

    Thanks!
    Last edited by MMMEAT; 05-14-2018 at 06:46 PM.
    Brian A Silverton, OR

    '85 Euro 635CSi 5 speed conversion
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    Unofficial 1995 BMW 540i MSport registrar (please see Facebook BMW 1995 BMW540i Msport registry group to join or report a sale)

  13. #13
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    24 STOP LIGHT SWITCH 4-POLIG/ELO 1 from 09/1992 61318356527 $144.29 http://www.realoem.com/bmw/enUS/show...diagId=35_0056
    Shogun tricks and tips for the E32 series are HERE!

  14. #14
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    Thanks shogun! ECS has for 132.00 free shipping..I think I'm just going to go for it, as intrigued as I am by the DIY Stovepipe cleanout procedure
    Brian A Silverton, OR

    '85 Euro 635CSi 5 speed conversion
    '87 L7
    '93 Euro M5 3.8
    '93 740i
    '94 850CSi #31
    '95 540i Msport 6 speed
    '96 M3/4/6 Euro 3.2l
    '03 M3 Cab
    '12 X5 3.5D Tuned

    Unofficial 1995 BMW 540i MSport registrar (please see Facebook BMW 1995 BMW540i Msport registry group to join or report a sale)

  15. #15
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    you could also manually clean it http://www.nmia.com/~dgnrg/page_25.htm
    Shogun tricks and tips for the E32 series are HERE!

  16. #16
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    I tried the high voltage cleaning the terminals trick first, but it ended up not being a reliable long term solution. The warning would keep coming back eventually. Most often on cold mornings. Sometimes immediately, sometimes only after driving the car a few kilometres down the road. Either way, it was highly annoying as the warning message won't go away again until you've reached your destination and switch off the engine.

    Eventually I got frustrated enough to buy a new switch and replace it. One good thing about owning a RHD in this instance is that the switch is one helluva lot easier to access as it's only behind the glovebox rather than in the footwell with all the pedals. I had to remove the glovebox anyway because the gas struts that extend it out toward the passenger seat are both completely knackered and in need of regassing or replacement. In so removing the glovebox, the brake switch became quite accessible too, so one job became two.

    I'm not so sure that cleaning the existing switch when the car has ASC is entirely practical. The difference in the switches between the standard non-ASC and the ASC version is substantial both in terms of price and construction. My car is ASC equipped, so I had to cop the expensive version which looks to be aluminium in construction and riveted inside an aluminium heat sink sleeve. It certainly does not look as easy to disassemble non-destructively as the plastic non-ASC version. I will give it a crack anyway with my old one just to see if it can come apart since I'm replacing it with an entirely new one.

  17. #17
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    Please help me. I started getting the Check Brake Circuit warning in the dash check control display. I tried the test light burning the brake switch contacts clean guide thing and it didn't work. Then I replaced both the bulbs and the bulb holders in the rear light clusters. That didn't work either. Yesterday I wasted $127 buying a brand new brake pedal switch and installed it and today that hasn't worked either. I am still getting this bloody Check Brake Circuit warning crap. Where do I go from here? I've wasted so much money and time on this non-existant fault now that I don't know what to look for next.

    Just to be clear, there is nothing wrong with my brake lights at all. They work fine. They light up bright and consistent on every press of the pedal. There is nothing, absolutely nothing to suggest from outside the car there's any fault whatsoever. My check control is telling complete & utter lies. How do I get it to stop?

  18. #18
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    Maybe it is time to check the CCM http://twrite.org/shogunnew/diagnosis/ccm.html
    Shogun tricks and tips for the E32 series are HERE!

  19. #19
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    Quote Originally Posted by shogun View Post
    Maybe it is time to check the CCM http://twrite.org/shogunnew/diagnosis/ccm.html
    +1 shogun. A failed solder joint in your CCM will prevent the brake switch signal from being seen by the computer. The brake switch pin is Green 7.

  20. #20
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    I've got the board out now and my Electrical & Electronics/Control Systems Engineer brother is on his way with his test equipment.

  21. #21
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    he also should pay special attention to the resistor group inside the CCM. Here another CCM repair from Germany which also shows the problem area R60 , R61, R62 http://www.e34-welt.de/tips_tricks/R...0e34%20e32.pdf
    R60,R61 and R62 are basically the measuring "feelers", and these resistors have to be resoldered.
    Shogun tricks and tips for the E32 series are HERE!

  22. #22
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    My CCM must be a later version because it doesn't have these resistor 'packs' as such on it. Visually, it doesn't look the same layout as the ones in the PDF images. My brother says it probably is the same electrically, it's just that it's all laid out and arranged differently. The resistors are all individual on the board and not arranged in 'packs'. The IC's are all arranged vertically, not horizontally and there are several other visual differences too. I'm guessing it's just a later version model CCM.

    What will dissolve the horrible red goo resin that's been sprayed all over the entire board? It's well near impossible to solder anything on the board through the red resin goo clogging everything up and regular contact cleaner won't budge it.

  23. #23
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    google for: how to remove conformal coating from circuit board
    I usually use option 3 from here, scraping https://blog.dymax.com/3-ways-to-rem...ormal-coatings
    3 Mechanical Removal
    Scraping or cutting the conformal coating may be an option for some applications and is easier with thicker, more flexible coatings. Pressurized abrasive systems- like micro-abrasive blasting- are often used to safely remove cured coatings. The abrasive is easily removed from the surfaces without danger to the components or reworking process. This technique is fast, cost effective, and environmentally clean. It also enables you to selectively remove the coating from a specific targeted area, while causing no damage to the surrounding components.
    Shogun tricks and tips for the E32 series are HERE!

  24. #24
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    Couldn't find anything obviously wrong with the board or the components on it. Tested all the resistors and they all checked out as being within spec. Have resoldered every connection on the Green 7 pin circuit and will now hope for the best. Back in the car now and taking for a test drive to see if it faults.

    Update: Taken for test drive with multiple stops to a trimmer about regluing some shrunk vinyl, to a hydraulics company about some SLS suspension component repairs & to mechanic workshop who will be removing said SLS suspension components for rebuild. No faults at all from the CCM so far. This is by no means an exhaustive test for an intermittant fault, but fingers crossed, it's looking good so far. Test will be tomorrow morning when I get up early in the cold of the morning and drive it to the golf course. If it doesn't fault in the cold of the morning, then I'll be a lot more convinced.
    Last edited by Legoman; 07-20-2018 at 05:24 AM.

  25. #25
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    I'm willing to tentatively call this fault fixed. It hasn't faulted once since I did the resolder of all the Green 7 pin circuit joints on the CCM board. Tip for anyone else in future reading this thread: If your car has ASC, then try this resoldering fix BEFORE buying a new brake switch. The switch for ASC-equipped cars is 4x the price of the standard one and that makes it a very expensive unnecessary purchase if the fault is not in the switch at all.

    Also, even if the CCM board looks absolutely perfect in every respect and you can't see any hairline cracks in any of the solder joints even with an illuminated magnifying head visor, it may still be at fault.

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