1997 540i completely died for a minute

[Q4269271]

I was driving home in a rain storm, and as I was nearing home, I noticed the tape player cutting out for a few seconds here and there. Then right as I was parallel parking, the car completely died. I'm not sure if it was because I stalled it, but usually when I stall it, all the lights stay on. This time, the car was completely dead. When I tried to restart the car, it didn't even click. It was completely dark. I only got the check battery and oil lights and a really faint backlight behind the instrument cluster. So I went to the trunk to check the battery connection, and before I could touch anything, the car's lights came back on by themselves. Then I started the engine, and it turned on with no issue.
I wanted to see if anyone here had any idea what happened? The car is ok now but I don't want it to happen again.
Thanks in advance

Here is some information I think might be related.
I suspect the car might have a faulty light control module because sometimes one brake light or one headlight randomly decides not to turn on, and occasionally the car randomly turns on the hazard lights, interior lights, and unlocks the doors.
The sunroof mechanism is broken, but the headliner and the floors feel dry.

[jicaino]

Time to check if battery terminals are clean, lubricate them with dielectric grease and torque them properly. Also this could be water/moisture related as you suspect. I have seen cars with severe LCM and electric distribution block (junction box under the passenger seat carpeting) corrosion/water damage still having dry headliners and apparently dry carpet.

Another source of this could be the ignition switch, but something tells me you have a passenger side leak that has corroded stuff on that side (LCM is under the passenger side's outer cowl side, like under the A pillar cover, which is plastic and funnels any sunroof cassette leak and sprays it onto the LCM as if the LCM was Mia Khalifa)

I would start with removing the passenger seat, lifting the carpet and checking those boxes, then check the LCM, then also verify your battery terminals are clean, lubed and properly fastened, but just foe good measure)

There's an out-of-this-world contact cleaner/deoxidizer called Caig DeoxIt. Really amazing stuff that works like sorcery for cleaning, removing that dark corrosion that forms over copper contacts and the whiteish corrosion of tinned terminals as well. It comes in spraycans of various sizes, brushtop bottles, and whatnot. They also make a battery terminal cleaner/lube that's just unbelievably good and I use it for almost all purposes too, like leaving a film over freshly restored ignition switches, for the alternator wires, for everything electro-mechanical. I only use the DeoxIt spray on the electrical/electronical wiring harnesses plugs, and then a dielectric grease. It is not the cheapest out there but let me assure you, it's the best. Tip: you'll find better pricing on Amazon than on their site (annoying trend that I've seen with many products, the official brand site having worse pricing and cranky nonsensical shipping stipulations)

[BimmrMeUpSnotty]

This is like a broken record and no one notices….

[jicaino]

This is like a broken record and no one notices….

My caig devotion you mean? It's really, really good.

[Q4269271]

Time to check if battery terminals are clean, lubricate them with dielectric grease and torque them properly. Also this could be water/moisture related as you suspect. I have seen cars with severe LCM and electric distribution block (junction box under the passenger seat carpeting) corrosion/water damage still having dry headliners and apparently dry carpet.

Another source of this could be the ignition switch, but something tells me you have a passenger side leak that has corroded stuff on that side (LCM is under the passenger side's outer cowl side, like under the A pillar cover, which is plastic and funnels any sunroof cassette leak and sprays it onto the LCM as if the LCM was Mia Khalifa)

I would start with removing the passenger seat, lifting the carpet and checking those boxes, then check the LCM, then also verify your battery terminals are clean, lubed and properly fastened, but just foe good measure)

There's an out-of-this-world contact cleaner/deoxidizer called Caig DeoxIt. Really amazing stuff that works like sorcery for cleaning, removing that dark corrosion that forms over copper contacts and the whiteish corrosion of tinned terminals as well. It comes in spraycans of various sizes, brushtop bottles, and whatnot. They also make a battery terminal cleaner/lube that's just unbelievably good and I use it for almost all purposes too, like leaving a film over freshly restored ignition switches, for the alternator wires, for everything electro-mechanical. I only use the DeoxIt spray on the electrical/electronical wiring harnesses plugs, and then a dielectric grease. It is not the cheapest out there but let me assure you, it's the best. Tip: you'll find better pricing on Amazon than on their site (annoying trend that I've seen with many products, the official brand site having worse pricing and cranky nonsensical shipping stipulations)

Thank you so much for the reply. Sorry if I'm reposting a common problem, but I did search around but I didn't know enough to connect the dots. This is really helpful, especially since I don't have a driveway or garage and am just pulling my car apart on the side of the road.
I pulled up the carpet and felt the area around the distribution box under the passenger seat, but it felt dry. I also managed to get to the LCM after snapping a ton of plastic, and the area also felt dry.
The box under the seat looks like this.
IMG_0772.jpg

I am going to fix the sunroof, buy that deoxit stuff, and probably replace the LCM.
Does the box under the seat look problematic? Could there be a problem anywhere else?

Thanks so much again

[jicaino]

That box looks minty and flawless. Maybe the LCM has decaying capacitors. If you can solder, maybe it's worth trying to open the plastic casing of the LCM and take a look there. Also, seeing that box, maybe the ignition switch gospel applies here. I've been passionately hating the trend of BMW parts now being outsourced to less prestigious markets, I would disassemble the one you have now and inspect it. It's fairly easy, and if you get the caig (or any contact cleaner really, but the caig has the added bonus of oxide removal) you may very well be able to restore it and it would be more reliable than subpar markets cheap units even if they're boxed in "BMW Group" labeled boxes. After all, one has only to see what BMWs are now to understand how the quality has decayed over the years