Intermittently faulty headlight - No CC warnings

[Legoman]

I have a weird issue with my 740iL I'm wondering if anyone has experienced before and can advise where you started looking. My driver's side low beam headlight intermittently switches itself off for no apparent reason an no amount of percussive maintenance on the lamp unit can get it to re-illuminate. There are absolutely no warnings or gongs on the Check Control instrument cluster display when this happens, or in fact at any time for any of the car's functions. When first switching on the headlights, they both illuminate as per normal and everything is fine, then at some point during my drive, the driver's headlight goes out. It's not immediately obvious to me when this has happened because the street lighting is good enough that you can't instantly tell when you've lost a headlight unlike if driving in the country when the headlights are the only source of illumination.

It becomes obvious when I pull into my garage and I can see the clear lack of a driver's side beam against the wall. I have got out and wiggled the wires, tapped on the glass lens etc. but nothing gets the bulb to light up again. Any ideas? I have not replaced the bulb because I figure it works when first turning the lights on, so it can't be blown in the traditional sense, right?

The bulbs are the bog standard Halogen standard issue ones that came with the car. There are no dodgy, Xenon aftermarket upgrades at issue here. All bog standard OEM stuff.

Thanks for any advice offered.

[shogun]

Maybe a LKM problem, had that too, see my pic here and how to test + fix http://www.bimmerboard.com/forums/posts/535192/
Low beam has 2 fuses, high beam only 1, check / swop fuses for test.
If that does not help, remove the black cover behind the bulb in the headlight from engine bay, where the plug goes in, inside there are 2 wires, sometimes they get lose and have to ve resoldered.
Here you see the 2 wires, at the bottom of the cap they are soldered https://www.ecstuning.com/b-genuine-...e/63121378333/
I once has installed H1 socalled rally bulbs with 100W instead of 55W, these 2 wires were blank and the plastic melted within minutes, even the reflector had some bubbles, had to replace the reflectors too.

If all that does not help, report back

[Legoman]

Found the fault. It's definitely the relay. Activated it by pushing on the trigger arm with a skewer stick and managed to get it so the left low beam was solidly lit while the right (driver's) was flickering. Cleaning up the contacts now to see if that fixes it temporarily, but what's the solution to replace the relay? Can these relays be sourced new from anywhere? It's that 018-01 one.
IMG_0955.jpgIMG_0956.jpgIMG_0958.jpgIMG_0959.jpg

[shogun]

we discussed that some years back on the German forum, conclusion was that as long as there are enough used LKM available, no need to source a relay. I do not know of a source of such relay at the moment.
Try to clean and rebend the contact arm, many do that and it helps in most cases.
Resoldering cold soldering pints, here pics from Japan
http://dd.jpn.org/BMW_HP/20051106/index.shtml
http://dd.jpn.org/BMW_HP/20040911/index.shtml
http://dd.jpn.org/BMW_HP/20110904/index.shtml
http://dd.jpn.org/BMW_HP/20101215/index.shtml

large pics of all 4 relays in the LKM, also the 18-01 http://www.e32-schrauber.de/bmw/s-lkm.htm
there you see the bad contacts of the relay.

[Legoman]

large pics of all 4 relays in the LKM, also the 18-01 http://www.e32-schrauber.de/bmw/s-lkm.htm
there you see the bad contacts of the relay.

That's the one my car's got. What I did as a temporary repair was to bridge the two (left + right headlight) contacts together with a strop of solder across the back of the PCB. The thinking being that if one contact is pitted and burnt (the driver's side headlight one), then the power current still has a second path to go down via the left headlight contact if I join them together. This seems to work. I can't see why they need to be separate supplies anyway, unless the CCM can distinguish between a left and right headlight globe failure? I really didn't bother investigating that before I did it because my main focus was on getting reliable working headlights, but it's of course conceiveable that I've ruined the ability of the CCM to tell me about a discrete voltage drop on either side of the car by joining the headlight's power supply together. I can probably live with that for gaining reliable headlights.

[shogun]

That is only on the low beams that there are 2 contacts and see also fuses for low beams, I assume just a safety measure that if one contact breaks, you still have at least the other low beam working.

[Timm]

They are kept separate so the CCM can detect which light has failed - the same is true for the fog lights (which is another two-pole relay) - and most of the other lights with the exception of the reversing lights and parking lights on some country variants.....

[Legoman]

They are kept separate so the CCM can detect which light has failed - the same is true for the fog lights (which is another two-pole relay) - and most of the other lights with the exception of the reversing lights and parking lights on some country variants.....

Yeah that's what I surmised would be the case. In that case then, my solution has stuffed this for the CCM. That said, in 27 years of driving it, I can honestly say I can't remember the CCM ever having to report to me about a blown headlight bulb, so I think losing this functionality is not going to keep me awake at night.