Brake, tail, number plate and dip light warning won't go away

[Reidal]

Hi All

New boy on the block. I have been through the forum but can not find any additional info so here goes hoping someone can help.

1993 E34 530i RHD 191k km's. Warning display for Brake, tail, number plate and dip light comes on when I switch on the head lights and won't go away until I switch the lights off then turn ignition off (short delay before the warnings shut down). No warning during the day (lights off of course).

I have read the info re the LKM and as an experienced electronics tech I can confirm I have re soldered all the relays (4 relay LKM) and LKM connector joints. I have also re soldered a number of through board holes and components (using hot air gun).

Absolutely no change. Problem persists. All the lights work correctly at all times.

Does anyone have any idea's?

[winfred]

theres a good chance the check control module (ccm) is dieing, on usa cars it's next to the lkm in the fuse box, someone here on the forum figured out how to test and repair them

[Reidal]

Thanks for the help Winfred.

I have searched for and found the CCM information and will give it a look tonight.

I'll confirm how thing go.

[Phil Sanderson]

Check the wiring on the left trunk lid hinge arm for broken and touching wires

[black_bird_blue]

I had a very similar problem to this - it was the headlight levelling motor seized up. I only found it because I had the lights on and engine not running and walked around the front of the car, I could hear the motor grinding away at some length. To diagnose the problem, I just unplugged the motor (near the bulb backs) and the problems went away.

Your mileage may vary, of course.

I recently replaced the motor and all has remained fine.

Damian

[Reidal]

All good input thanks guys.

I have checked the CCM carefully and can find no circuit board fractures and all the components appear to be OK. Some solder joints looked iffy but checked out electrically OK (re-soldered anyway just in case).

Moving on to the trunk (We Aussies call it the boot by the way) hinge wiring this weekend and will also check out the headlight leveling motor while I'm at it.

I must say it is fun to be tinkering again after many years in Japanese clones (although I might feel differently when I have a major melt down).

Also ordered a Bentley on Amazon ($83 USD opposed to $200 AUD locally)today, so I will be able to go in depth if this week end is unsuccessful.

[Unregistered]

Hi...

Mine is also a RHD 530iA '96 and I also experience exactly the same symptoms as yours.

BTW, I've gone most of the forums suggested, such as making sure the bulbs are of the high quality brands and they are of the same types, and checking the wires on the left side of trunk door. Furthermore, these are few more things I did :

1. Add ground cables from each of rear lamps (including reverse light and licence plate ligths). The new ground cables go directly to the (-) of the battery. I suppose the problems was due to bad grounding.... IT WASN'T... Helps a bit.

2. Change both LKM and CCM. I swapped with the same car (530iA) with the same year. My old LKM and CCM don't do any trouble in the new car. But the nasty false alarm still ding in my car..

3. Resoldered LKM. Furthermore I added reverse polarity diodes to the primary side of each relay (in case there is wild reverse current). Helps a bit, but not solve problem.

4. Putting reverse polarity diodes onto the troubled lights (lic. plate, tail, brake and low headlights) to fight wild reverse current. Still not solved.

5. Maybe I am going to put some high capacity capacitors such as used in the high powered sound amplifiers, because I am still believe that the problem is bad connection somewhere, and the only place I haven't looked at is the power (pin 2 on the LKM).


I am very curious to solve this problem. At least I am 'happy' to find someone with exactly same problem. Even the stealer hands up about this.



Eri.
530iA '96
53000 km overall.

[Phil Sanderson]

On my car, for some unknown reason, the wiring loom was cut where it passed through the metal wall behind the back seat to underneath the back seat. It was my reversing lights that were intermitently coming on then off. With to boot/trunk lid closed the lights worked but when I opened it it tugged on the wiring loom and split the reversing light wire under the back seat. I know this sounds odd because the wiring loom is attached at the hinge and in other places, but it can still move. My car is an '89 525i - on cars with battery under seat, the wiring loom will come through right behind the battery - I suppose.

Phil

[Ian W]

I have a 94 rhd 530, that does the same. The symptoms may be slightly different as brake, number plate, dip, warnings only come on when I have the lights on and apply the footbrake for any length of time.

When I got the car it annoyed me so I changed all the bulbs to bmw which did increase the time it took for the warning to come on.

I presumed this was just the brake switch , but I've never got round to replacing it.

Glad I've got used to it, if it turns out tricky to fix.

Good Luck

[Gary M]

You might to want to check and clean the contacts where the bulbs plug into the lamp assemblies. They corrode over time and sometimes cause problems. Although I don't know if it would be the same type of problem you're experiencing.

[Reidal]

Guys, thanks for the replies. I was begining to wonder if I was the only one.

I have not yet found the answer either. Since my last post I have:
1) checked the trunk hinge wiring (looks ok)
2) been around all the bulb connections with a fibreglass cleaning pencil
3) checked the rearward wiring through the back of the trunk

I have now begun to pick my way through the wiring diagrams to try and work out where all these lights have common circuitry. The odd one out is the dip beam, which makes me think it must be the LKM or it's feeder wiring or alternativly, a positive power feed/fuse etc.

I'm hoping this one won't beat me :(

[Elekta]

I had a very similar problem to this - it was the headlight levelling motor seized up. I only found it because I had the lights on and engine not running and walked around the front of the car, I could hear the motor grinding away at some length. To diagnose the problem, I just unplugged the motor (near the bulb backs) and the problems went away.

Your mileage may vary, of course.

I recently replaced the motor and all has remained fine.

Damian

It kills me that this was my issue for my warning woes. I had changed both my rear wiring harnesses, my brake light switch and my license plate lights before my indy started on a test rampage that indicated my headlight levelling motor was causing the warning.

I still have my old touring harnesses with rear fog lines in a box in the attic.

Hey, when are we going to see your 540iT? get a photobucket.com acct and host some pics whydoncha?

http://volcano.photobucket.com/albums/v11/ggil-tx/bmw/DSCN0958.jpg

[Reidal]

Hi Guys

The top score goes to Damian and Eri for highlighting the Headlight leveling motors (but thanks to every one else for their valuable input ;) ).

I carefully checked them some time ago and found they worked perfectly. Twiddle the knob, headlights go down. Twiddle the other way and headlights go up.

Ahh I thought, these are not the problem (WRONG).

Revisited and this time disconnected the motors. Warning lights have not reappeared in approx 3 hours of night driving where they would appear within 15 minutes previously.

I will now try and work out how apparently perfectly operational motors can cause the spurious warnings experienced. I suspect electrical noise is being fed back into the lighting circuits from the motor commutators.

Thanks again Guys. I know my car far better now than I did 3 weeks ago. :)

[Elekta]

I will now try and work out how apparently perfectly operational motors can cause the spurious warnings experienced. I suspect electrical noise is being fed back into the lighting circuits from the motor commutators.

Let us know what you figure out. I thought I was leaving perfectly functioning light levelers disconnected just to get rid of an error message.

Mine are still disconnected

[Unregistered]

Hi Guys

<DELETED>

Ahh I thought, these are not the problem (WRONG).

Revisited and this time disconnected the motors. Warning lights have not reappeared in approx 3 hours of night driving where they would appear within 15 minutes previously.

I will now try and work out how apparently perfectly operational motors can cause the spurious warnings experienced. I suspect electrical noise is being fed back into the lighting circuits from the motor commutators.

Thanks again Guys. I know my car far better now than I did 3 weeks ago. :)


Hi Reidal,

definitely it's some electrical noise that did it!!

Just yesterday I changed my alternator, and..... the stupid false alarm still exist..... My last theory is that the alternator (or the voltage regulator to be precise) cannot maintain the minimum voltage level or cannot produce smooth direct current. However, it's wrong.

I will try to disconnect both headlight levelling motors, and lets see how it works. Anyway, I just beginning to think the aux fan motors is the most probably culprit because it's the only motor consuming the most current. I will try to cut off the aux fan while driving at night (hope it will not turn the stupid false alarm on).


Eri.

[Unregistered]

Hi i have a UK E34 520i (01/93) with a wierd problem!

I have no drivers side sidelight, taillight or number plate light.

I've checked all the fuses and connections, and then went hunting for the LKM, which I cannot find! i've checked the fused box carefully with the pictures off E34.net but it' looks nothing like!#

Help, please before I end up getting spoken to by the nice policemen

[lotus88]

Hi i have a UK E34 520i (01/93) with a wierd problem!

I have no drivers side sidelight, taillight or number plate light.

I've checked all the fuses and connections, and then went hunting for the LKM, which I cannot find! i've checked the fused box carefully with the pictures off E34.net but it' looks nothing like!#

Help, please before I end up getting spoken to by the nice policemen
Hi there, I have the same problem, if you find out where the LKM is can you let me know too as I want to tackle mine this evening

[Unregistered]

Hi Lotus88,

Yes I will, I hold out no great hope though!

'local dealer is as helpful as mud, and Haynes make NO!! manual for these cars!!!-Unreal'

Bob1004

[lotus88]

Hi Lotus88,

Yes I will, I hold out no great hope though!

'local dealer is as helpful as mud, and Haynes make NO!! manual for these cars!!!-Unreal'

Bob1004

Hi Bob, Haynes do make a manual that covers both the 3 and 5 series cars but it is really a complete waste of time. You can download it for free froma Russian web site. It lloks like we have the same problem with intermittant low beam, I am going to take my LKM out tonight if I can finf it and solder it up. I will let you know how I get on.

Peter

[Unregistered]

Hi Lotus,

Yes, I bought the manual for the 3/5 series after speaking to haynes on the phone...took it outside halfords, read it, took it back!

If you do have any luck in finding the bloody thing let me know...I also tried the 'stomp' test today and found that it doesn't work either... ;-(

bob

[Unregistered]

Hi Lotus88,

I HAVE LIGHTS!!! YIPPEEEE...

Took car to garage, mechanic said that my car DOES NOT have an LKM module and that BMW are prone to doing such things.. Apparantly they 'hide' them in either the front left fusebox, the front right 'fusebox' (same opposite side), or the one in the rear under the seats.

Mine was fixed by the checking and repair of the boot wiring loom which was damaged (according to the mechanic, its a 'common enough thing') and he resoldered ANY joints he came across, cleaned up all the contacts (bulbs, relays etc) and hey presto it's all ok..

Hope this helps?

Cheers ppl,
Bob1004

[Unregistered]

Many thanks to Reidal, Damian and 530iTouring.

Mine is the left side Headlamp Levelling Motor. It's working perfectly, without grinding sound or whatsoever, and still in original sealed condition. Some time ago I did a service to the right side Leveling Motor, but it wasn't the cause in this case.

Now it's the 5th day it's disconnected, and NO single false alarms came on...

Just wondering, what's wrong with the Headlamp Levelling Motor that cause this very stupid false alarms ?

Eri.

[system11]

Hi Guys

The top score goes to Damian and Eri for highlighting the Headlight leveling motors (but thanks to every one else for their valuable input ;) ).

I will now try and work out how apparently perfectly operational motors can cause the spurious warnings experienced. I suspect electrical noise is being fed back into the lighting circuits from the motor commutators.


This is exactly the problem my car currently has, although pulling the LKM and cleaning the contacts made half of the warnings go away. Did you ever resolve this fully?

[Reidal]

I have to admit to a degree of laziness on this as I have not sat down with scopes and meters yet (also been busy with Oil pumps and cam chains).

Just after I worked out that both leveling motors were causing the issue, I had to replace the battery.

Ah ha I thought :p , failing batteries often exhibit hi internal impedance which means the current drawn results in an increase voltage drop across the battery terminals (hence the failure under load).

This can also upset the batteries ability to act as a short circuit for electrical interference throughout the system which means the noise becomes more noticeable to things like OBC and sound systems.

Wrong :( Reconnected the leveling motors a couple of weeks ago and immediately the warnings popped up again.

So it's back to the drawing board. I'll try and do the scope and meter thing over the next few weeks before the weather here in Melbourne gets to good to do more than laze by the pool sipping a good glass of red.

[ewidjaja]

I got the idea that the Leveling Motor cause the problem from this thread back last year. From that time, I just remove the Left side Leveling Motor connector from its wires.

Last weekend, still wanting to know what causes the various Light Failure Warning false alarms...

I decided to open (literally) up the Leveling Motor assembly. I carefully pry it open (hammering using small (-) screwdriver). After it's open, I see the motor, and a small PCB (printed circuit board). And, aha..... there is a tiny electrolyte capacitor rated 33 uF / 25 V / 125 C. I think it might be the problem, faulty capacitor can fail to filter unwanted noise from the motor itself. But I don't have the same capacitor rating. So, I decided to solder it out, and replace with whatever I had (100 uF / 16V / 85 C). Then I reassemble the pieces and glue both clam shells of the Leveling Motor to ensure it's water tight.

After putting in everything together and connect it to the connector, then try to run the engine and turn all lights and equipments on... and the false alarms just vanish......
:) :)

Eri.
just very happy to save my Headlight Leveling Motor ;)

[Elekta]

Did you take pictures of this endeavor? I too would like to restore my headlight leveling motors.

I finally disco'd the motors after replacing the two touring rear wiring harness year and a half ago. doh

[Reidal]

Well done Eri.

I may look at doing this as well now that you have given us the lead.

If you have not got photos' let me know and I will make sure I document the process when I do it.

[ewidjaja]

Sorry Reidal and 530Touring,


I didn't take any photos.... But it's straightforward.

1st you need to take out the Headlight Leveling Motor (I think you must know how to do it).

Then you look at how 2 plastic shells joined together along the Leveling MOtor body. I pried this line using a tiny (-) screwdriver hammerred into it. Be careful in doing this so not to break the plastic shells.

After they are apart, carefully open it, and see only 1 electrolyte Capacitor soldered in the PCB. Desolder it, and change with new one. Be careful in changing Electrolyte Capacitor because they have different pole (+ and -) and don't put the new in wrongly.

After that, reassemble everything, and put some glue (I use 5 minutes Epoxy adhesives, the one coming with 2 tube -- Epoxy and Hardener -- and we need to mix together and it will harden in 5 minutes) to make sure the join is watertight. Oh yes, when gluing it, I tie both plastic shells with a tiny nylon to make sure the join is tight.

Good luck... And share how you are doing.


Eri.

[NJHokie]

Does only the tourings have headlight leveling motors or the sedans as well? I have a 91 535i and i'm experiencing the exact same problems.

[wingman]

On my car, for some unknown reason, the wiring loom was cut where it passed through the metal wall behind the back seat to underneath the back seat. It was my reversing lights that were intermitently coming on then off. With to boot/trunk lid closed the lights worked but when I opened it it tugged on the wiring loom and split the reversing light wire under the back seat. I know this sounds odd because the wiring loom is attached at the hinge and in other places, but it can still move. My car is an '89 525i - on cars with battery under seat, the wiring loom will come through right behind the battery - I suppose.

Phil

Phil,
This is an old post I know but was this problem causing your 'lic.plate.light' warning to come on? I've had the lic plate lights coming on when opening the boot for a while now but now I'm getting a dash warning. I've changed the globes to no avail.