Instrument cluster LCD pixel repair (sequel to "Return of the Pixels;" part 4) e36 m3

Описание: This is the last video on this topic (quite certain now!) While I thought I found the faulty pin solder (pin #22 in minute 8:50 of this video):
   • The Return of the Pixels: Third installmen...  

It turns out, that it was indeed the most damaged solder (but not the only one), hence, 95% of time I could see all pixels fine. But I am not about 95% perfection, I aim for 100%. So I opened this instrument cluster a fifth time and I was able to identify the second most persistent faulty pin (#7) (0:00 - 1:10 min of this video). Even though, I could have fixed pin #7 (and hoped for the best), I decided to open this cluster a sixth time and remove the "protective coating" on all pins, and re-soldered all 45 pins (even the ones that are clearly not connected; they aid in holding the LCD housing firmly in place). It is clear that other pins were next in line of culprits, and could have started to lead to intermittent faulty contacts, and hence I wanted to get the job done right. What held me back all this time was my hesitance to stripping the protective coating (since I did not want to damage the PCB board; you can see it was badly scratched from my attempt to remove the coating, but luckily it did not impact operation).

Just remember this video is NOT a standalone video. It is an addendum to the previous complete videos:

Short: (10 minute):
   • The Return of the Pixels: Third installmen...  

Long version (23 minutes):
   • The Return of the Pixels: The third instal...  

SUMMARY OF ALL 6 ATTEMPTS: (only unplugged battery on attempts # 2 and #3; not necessary as long as you do not have the key in the ignition when the airbag is disconnected)

1. Added a foam spacer behind the metal clip of the LCD screen (helped temporarily)
2. Cleaned the contacts behind LCD screen better and replaced the deteriorated foam space with painters tape (helped a bit more; but not entirely)
3. Cleaned the LCD rubber connector and metal contacts even better. Drilled pegs that held PCB board; discovered coating on pins which appeared in good condition (chickened out and put it back together)
4. Tested pins by pushing on them while the key in either position I or II (make sure your air bag is also connected at that stage or you'll get the airbag error code); identified pin #22 as a cold soldered one, so removed its coating and re-soldered (this helped bringing to near 95% perfect)
5. Realizing there were more damaged solder joints, probed and identified pin #7. Did not remove coating, just tapped 280 °C soldering iron on all pins hoping to remelt the solder a bit so it fixes cracked joints (clearly did not improve operation that much; still at 95% perfect)
6. Decided I needed to remove the coating entirely and re-solder all pins. I did. It is perfect NOW - 100% (and I confident it will remain for years to come!)

In conclusion: The intermittent LCD pixel faulty operation is a result of poor electrical contacts. There are two possible places of potential poor contact. 1) LCD rubber connector to the metal contacts in the white housing 2) corroded and/or cracked solder joints at several of the 45 pins. The former seems to be a bit less prevalent. Most times, it is the soldering contacts (which are clearly machine generated and have minimal solder in them; so with time they corrode and/or crack). In my case, I believe I had an issue with both, but certainly mostly with the solder joints. So If I only addressed the solder joints, would I have needed to still add the spacer and scratch the metal contacts behind the rubber zebra connector? Well I would never know now; and that's ok! It works - I learned a great deal!

ACKNOWLEDGEMENTS:
Special thanks to all who guided me and commented on my earlier videos and replied to my questions on their videos. This includes the following people/channels in the order of help received or video reviewed:

23tlujan23
Geoffrey McEvoy
Pixelfehler Hamburg
Francesco ’s BMW Kanal
Fischers Garage

Disclaimer: This video is for educational purposes only and I hereby release myself from ANY liability for any damages you may incur by attempting any of these procedures. If you are not comfortable working on your car, please seek professional help. This clearly requires specific tools and comfort with soldering. Improper procedures could lead to injury and/or potential issues with your airbag system.