W203 Electrical Problems

[CaptainVik]

Hi All,

Long time Lurker here, but now posting to ask about some electrical issues I've been having.

On Friday evening, my rear indicators went off (just them, flashing as though the alarm was triggered), and I was unable to turn them off with my key fob, I had to open the driver's door manually and insert the key into the ignition to turn the system off, and then after locking the car remotely, the issue started again. In addition, I noticed that the blue high beam light on the dashboard was also lighting up randomly.

I tried to start up my car, and everything worked fine, the engine started smoothly the first time, so I just locked it manually with the key and left it overnight and assumed that the problem was a rusting alarm siren which I can just deal with later.

My sister came to visit yesterday so I went to the railway station to go get her, and whilst the drive to the station was entirely uneventful, as I was on my way home, I had a complete failure of my electrics - I was unable to indicate, my radio failed, my climate control fan randomly started speeding up and slowing down and I started getting all sorts of error messages on the dashboard. Given that to get out of the railway station area in Oxford, I have to deal with about 5 roundabouts, you can imagine why not being able to indicate is a bit of an issue. Furthermore, the high beam randomly started flashing, which added to the roundabout mayhem....

After pulling over safely and turning the car off and on, it seemed to fix the problem but I had the same electrical failure in the centre of town a bit further away and I only just managed to bring the car home.

Now, my question is - could all of these symptoms still be consistent with alarm siren failure? If I were to disconnect the siren or its related fuses, would my car be functional? I'm currently a university student in the middle of finals, so I don't have a lot of time to go take it to a garage (nor do I have a lot of spare change!) so if I can get a temporary fix and get the car back to Yorkshire with my 'rents after exams, I can look at getting it fixed there, but that is 170 miles from here....

Any ideas would be wonderful!

Car: 2004 pre-facelift W203 C180K classic

 

[CaptainVik]

PS: Apologies for double post, I can't seem to find the edit button.

I forgot to mention I have an OBD2 device and it returned the "P0600" fault code.

In addition, the dashboard is consistently giving me the error: SRS Restraint System Drive to Workshop"

It does however, start and drive normally, with no loss of power or juddering or mucky idle speeds.

 

[curious]

Your symptoms would suggest a SAM is playing up.

I had all sorts of random electrical problems when my rear SAM went down. It seems catastrophic when it appears as if the whole car has gone wrong but, if it is a SAM, it's easily fixed by component replacement. Mine was fixed under warranty so I've no idea of the cost involved.
The SAM failing is a relatively common event for the 203.

 

[umblecumbuz]

I second Curious' diagnosis.
It would seem to be a front SAM failure. I have recently changed one on a W203 cdi because of a whole array of random symptoms that more or less mirror your experience.
Not a difficult job, but if you intend to do this, make certain that the repalacement has the identical part number.

 

[television]

And another for a SAM problem, the main problem is the 2 SAMs talk to each other so what one ?? If the siren does not work, then disconnect it as this can upset the car.

 

[CaptainVik]

Thanks for your help guys! I looked into this and it seems you are probably correct about that! I suspect the alarm siren is also naff but that's something that can probably wait.

I too was wondering how to tell if its the front or rear SAM given they talk to each other. Unfortunately I don't have the expertise (or the time) to try and source parts and repair it myself, and from what I read, they need to be exactly identical or they won't work.

Do you guys know roughly how much it'd be to get a garage or indie to do it for me? Or would it be worth taking it to Mercedes? The car itself probably isn't worth more than £1.5k - 2k so I'm toying with whether it's worth attempting to get it fixed or swallow my loss and get a new one down the line...

 

[turbopete]

as Malcolm suggested, do try disconnecting the alarm siren before assuming that its a SAM issue. if theres no change then STAR should pinpoint which sam has the issue

 

[M80]

When I had similar some years ago it was due to water getting in around the windscreen and onto the light switch wiring.

 

[CaptainVik]

Thanks Guys! I'll give that a go soon and let you know how it goes.

Just to clarify, in UK cars, is the alarm siren on the left or right hand side? And is there a fuse that I can take out or should I just pull out the alarm and leave it like that? (or do I need to have a spare ready to install)?

 

[curious]

The siren is behind the nearside wheel arch. Just disconnect.

Threw mine away years ago after it played up (dying battery).

 

[umblecumbuz]

If you ask MB for a sam price you'll be shocked. And you will probably also find that, unless they also fit it, they will not give you any warranty.

There are several outfits that will supply a sam, reconditioned, with warranty.