Dipped headlight not working. Kind off

[Stampee]

So I have no Dipped lights. However I do under some situations. I’m puzzled.
on auto or lights on theres no dipped lights , main beams work. but the dipped do flash sometimes, basically nothing then both flash a few time together then nothing again. If I shut the car down the dipped lights come on with ignition off and key in.
I just recently replace the ignition and keys as it failed leaving me stranded . I did a lot of checks with a meter and found nothing but wonder if I’ve damaged something somehow . Car now runs but I’ve an airbag fault and this lights fault , found a blown fuse for airbag but guess the computer will have now have logged it and must be cleared via diagnostic tool. The lights have me baffled .
if they work when it’s shut down then guessing all wiring is ok and bulbs too. Sometimes I start the car back up and they stay on but then I’m back to square one when I turn ignition off and lights again. I’m looking at a component issue I guess. I really hope not an expensive one .

 

[Botus]

this seems much like another post going round this weekend.

modern cars have control units to make sense of what parts of the car should do.... I like to think of them as posh fuse boxes with a programmable brain and a fault memory. It allows the manu to enable and or operate certain features depending on the build spec of an individual car. On a Merc these are called a SAM (signal acquisition module). Often a big black fuse box under the bonnet (sometimes with another at the back of the car). It is quite common to age and or fill up with water and then behave strangely....

The behaviour you have is indicative that the front one may not be happy.... Key off lights work, will be the illuminate so I can find the path / front door feature, (which you say works) but the show me the road I'm driving (doesn't - is what you say above). As its working one way and unreliably the other, I suspect it points away from wiring issues, towards the SAM or a relay doing its nut

First stop
Carefully check if the SAM is full of water (often are - and sometimes get over themselves with intervention, it can be an 8" deep bucket beneath the fuses you see laying flat on the top of the box) - if it is wet, I'd disconnect the battery and get the water out, dry fully, clear the drain, and try to remove visible corrosion (with contact cleaner and a toothbrush) and remake connections with WD40 or ACF50 everywhere on the circuit board and connections.

Then make sure its battery is charged fully, do some basic integrity checks of the wires to the bulbs (as its charging), then see where you are then try and read fault codes (but anticipate lots of muddled rubbish if the SAM is failing / was full of water). Wipe the codes its just rubbish and the real ones will pop straight back and if the SAMs functioning correctly you have something more substantial to work with

 

[mersum1es]

You are not saying what 2003 model you have... C, E, S, Vito....?


Try to cover light sensor...?

 

[Botus]

the poss related post... https://forums.mercedesclub.org.uk/index.php?threads/auto-lights-odd-behaviour.190622/

 

[Stampee]

Thanks all . It’s a 2003 w203 2.2cdi C Class estate (classic)
I Had battery out all day on charge. , removed front SAM to look for anything obvious. Nothing found. Though now it also says seat not locked?? Also rear wiper not working but that’s rear SAM ?? . It’s now also telling me to check front right and left dipped bulb which it didn’t before even though the lights issue was there before .
so now I’ve 4 faults showing . SRS, seat not locked . And left and right dipped beam bulbs. Lights still come on if the engines not running the go off when started and randomly flicker every 15 seconds or so.

 

[Botus]

battery removal might have got airbag module to lose the plot - we've had a few where silly messages pop up on aging modules and don't like to go away - some have lost the vehicle info from the module and the only way to force that back is to use dealer stuff and try and or replace...

what diagnostic kit have you got - they are not all created equal, quite a few cheap ones make stuff up. So long as you have a record wipe it and see what came back - lots of cars with old batteries / limited history are full or lies and junk of no use to anyone

lots of silly stuff can be old mildly oxidised connections, making and remaking connections by plugging and unplugging multiplugs and popping fuses back in an out (with some eleccy suitable anti corrosion stuff) is a good idea on old cars... especially with can bus mess.... it only takes a gnatts wotsit to throw lies and confuse

 

[Stampee]

battery removal might have got airbag module to lose the plot - we've had a few where silly messages pop up on aging modules and don't like to go away - some have lost the vehicle info from the module and the only way to force that back is to use dealer stuff and try and or replace...

what diagnostic kit have you got - they are not all created equal, quite a few cheap ones make stuff up. So long as you have a record wipe it and see what came back - lots of cars with old batteries / limited history are full or lies and junk of no use to anyone

lots of silly stuff can be old mildly oxidised connections, making and remaking connections by plugging and unplugging multiplugs and popping fuses back in an out (with some eleccy suitable anti corrosion stuff) is a good idea on old cars... especially with can bus mess.... it only takes a gnatts wotsit to throw lies and confuse

Thanks all. Ok so I’ve just got an icarsoft CR pro. I’ve had too many random issues since replacing the ignition module and key. . Rear wiper not working. Electric windows weird. Driver module only works drivers window. Front passenger window switch operates driver window. Rear work from rear door switches as normal . Front dims work until engine is running. The just flash randomly. Brake lights don’t work. SRS airbag system fault ongoing. I’ve got another front Sam unit. Not fitted yet. Is there’s anything I should be worried about. The ignition and key stopped talking.the drivers window was down at the time. I found a few fuses blown. There was a storm and I think water Got to the fuses on the drivers side.

 

[Botus]

if the part has the same numbers (and or a later one for that same model), then you should be able to get it to work...

however, it depends on the age and toy count, quite a few seem to have success on early cars exchanging for one from another car.... but that tends to be because back then, the same toys went on many cars so it might just be "coded" exactly the same (aka setup to operate the same toys the same way) - thus they appear plug and play

as cars became far more complex, with far more options, and then with another step change with high end options, the modules and or the software can be different, (on some brands there were budget units and posh units.... with the right tools the posh ones can work any car in the range when coded appropriately (allowing part bods to only hold the high end unit and not 4 different ones). Mercedes tend to have a different unit rather than a high end one you can configure to budget spec toy count.

So you could try and plug it in (if you think its closes enough to the one you need) and see where you are... but if somethings aren't operating its unlikely you can resolve at home... the next step on from good diagnostics cover, is a far more expensive tool that can do two way comms and code features on and off....

and if you buy brand new its no use to anyone as it has no software to operate anything (yet)

£200 mark allows use to have a clue what's wrong
in the old days it was around the £3000 price point to actually break lots of brands of car
of course fake dealer kit is often the nicest way to make progress "coding" and single brand merc stuff comes in around £300 for something nasty or £900 for something as good as the dealer has... BUT the software to push updates and do everything thing is still hard to come by... and Mercedes try to do with online with SCN (where it dials home and tells you what the car needs and then authorises you to break it)…. £10k a year...

 

[Stampee]

Thanks . I actually had a reply back from the guy that supplied the New EIS and it was for a right hand drive. And I need to get it coded correctly. As mine is LHD So I hope that will stop the SRS airbag and maybe resolve a few other issues. . Brake and tail lights, rear wiper, window control, dipped lights . So many random faults it nuts. But it’s out of my league and I don’t have the kit. Much prefer playing around with my old triumph then theses over complicated electronic nightmares. Having no car is becoming a real issue . But I really don’t know enough about these , EIS, SAM units . Completely lost.,