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Discussion Starter #1
Wanted to share my recent work regarding how to address a failing Light Kontrol/Control Module. Such a thread undoubtedly exists elsewhere, but here's my take.

My symptoms were a headlight (driver side) that wasn't quite as bright white as the opposite. Also, when I turned on the high-beams, it turned that, driver side, dimly lit, low-beam, off completely, and that same side (drivers) high-beam wasn't as bright either.

I noted the lights changed when I popped my hood. All the sudden all lights came on.

Something worth knowing, a faulty/failing/partial/semi-broken solder connection raises amperage on that circuit along with resistance. So letting it go, can, and usually does, do further harm to your electronics.

On to the show.... :thumbup:

Component side view:


Relays view #1:


Relay view #2:


Connector Close-up Component Side:


Side you'll work on:


Pins Close-up:


Pins Close-up #2:


Pins Close-up #3:


Short Video showing solder re-flowing pins
(I know, camera position made it vertical... Sorry)

Something to note: Right before the video ends, and just before I move the camera up trying to center the work, you should see the solder retreat downwards toward the other side of the board. This is really the only reason for the video.

I wanted to illustrate that if you just re-flow what you see, you can still end up not fixing what you're there to fix. When that solder flows back toward the other side, it greatly increases your chances of never having to revisit this. As you can see by several of the pictures above, the actual connections to several of those pins are on that back-side to what you're actually working on.

https://youtu.be/m9ykKJn8Bfo

Couple final notes: First, the shiny area/half of the board is all low power control circuitry, so there's really no need in most cases to worry about that side. The main focus of your work will be on the large connector pins, and the relay pins. Lastly, I washed my board with flux removing soap and de-ionized water. We're not dealing with a lot of signal clarity here, only power throughput. IOW, a couple q-tips and some alcohol to clean up residual flux is a good idea, but as long as there aren't any puddles between pins, you'll most likely be fine.
 

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Discussion Starter #2
Oh, forgot to mention something on soldering irons. I first went at this with a 50 watt iron at home. It worked for the most part, but struggled to keep up when I re-flowed the large puddles of solder and corresponding pins. The video is of me doing it with a moderately expensive 90 watt iron. Point is, a small pencil iron from a local home improvement store might take some extra time when heating the solder connections. Just be patient, and count the dollars you're saving.
 

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When you send an ECM, PCM, ECU or any other print board out for a rebuild what they usually do is brush on flux to all solder points and then go over it with a heat gun to reflow the solder at all of the printboard solder points. They do this before replacing major components because there is a 70% chance it'll fix the problem.
 

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Discussion Starter #4
When you send an ECM, PCM, ECU or any other print board out for a rebuild what they usually do is brush on flux to all solder points and then go over it with a heat gun to reflow the solder at all of the printboard solder points. They do this before replacing major components because there is a 70% chance it'll fix the problem.
I agree that is sound method, but then there's finding a processor that can do it in an efficient time frame (not including the shipping cost or duration), and what does that kind of work cost?

Don't get me wrong, soldering technique is definitely learned via familiarity with your tool, and trial/error. IMHO, it's not difficult at all, but I've been soldering things you need a loop under a magnifying glass, just to see, for more than a couple dozen years now. So obviously my opinion is somewhat moot.

Anyhow, if you can get your hands on a ~50w+ iron, some solder, and patience, here's a map: (By the way, I also hit the small surrounding components, but they truly did not appear to need the attention. They're just in a higher stress part of the board, so it's not a waste of time)

 

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ImageUploadedByBimmerApp1476463479.808031.jpg
What year/model is that one out of? Mine is a 1990 Luxury model 525i and looks nothing like yours. I did however get it working. Wasn't hard to just look at it and find the cracked solder points that needed redone.
 

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Discussion Starter #6
This is in my 1995 540i (MFG 10/94)



 

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Discussion Starter #7 (Edited)
View attachment 579146
What year/model is that one out of? Mine is a 1990 Luxury model 525i and looks nothing like yours. I did however get it working. Wasn't hard to just look at it and find the cracked solder points that needed redone.
Looking at yours, I'd solder all the same points really. It's generally going to be about the connector associated solder joints.

Edit... BTW, what does the other side look like? Picture?
 

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Looking at yours, I'd solder all the same points really. It's generally going to be about the connector associated solder joints.

Edit... BTW, what does the other side look like? Picture?
I did solder all the points just to be sure. Didn't feel like dealing with this again!
 
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