W220 320 CDI - Car sometimes needs closing twice (keeps blinking)

Irresistance

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1988 W126 420SE, 2006 W209 200K & 1999 S210 320CDI
Okay... well - I have had this issue since I owned the car but I am slowly starting to have enough of it...

The car will sometimes (more often than not) require me to lock it twice - after the first lock signal it will close, but the orange lights will blink like the alarm went off. No sound.

However. Just a month ago, by accident, while my mechanic had it on STAR, I noticed a "F" with the alarm system. Turns out the movement sensor on the roof was faulty. After a brief inspection, it became apparent the damn thing was not actually attached to the wiring... I re-attached it, and it seems to work. When I move around in the car when the alarm is engaged, the lights start to flash. But there is no alarm sound, like the horn is not attached or working.

Now - the previous owner had some other/second alarm system in the car, this has been removed over a year ago. The double-close/lights flashing problem was present before and after removal.

What is causing this? I suspect that if the alarm siren was working, the car would in fact be making noise in those instances where I need to close it twice...? Why is it doing this? What is it trying to tell me? I read somewhere here that the batteries on the alarm unit fade and thus cause problems...? But when I go look for anything alarm-related online I can only see three parts: Alarm control unit, the siren, and the roof sensor. No mention of any battery pack. Is this inside the control unit?

Many thanks :)
 

Oarsman

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W221 S350L CDI Bluetec, Range Rover Vogue SE 4.4 TDI, 1963 Triumph TR4
Yes, the backup battery is inside the alarm unit. The alarm is mounted behind the wheel arch cover on the nearside, between the wheel and the door.
It usually requires a replacement alarm unit, as there tends to be corrosion on the circuit board.
 

television

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Exactly as Oarmans post, many unplug them when they fail as they can blow the fuse in the boot.
 

AdamG

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S320CDI (2003)
I have had this annoying "feature" on my w220 since I've owned it.

I believe it is referred to as an optical alarm in WIS.

I have changed the siren but this did not make any difference.

I started a thread about it a few years back but with no solution

http://forums.mercedesclub.org.uk/showthread.php?t=75201

I think I read somewhere (probably wrong on this) that it is a feature specified on Belgium cars. I wonder if the alarm system was set to the U.S.A it would prevent it.

In Star the alarm trigger event is show as the siren.

Cheers

Adam

P.S please update if you make any progress with the shudder Fixx on the vibration problem
 

888s

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I have this exact problem! 2004 s320 cdi. Came back to the car one day to see the signal lights flashing but no sound. Had trouble turning it off when locking the car as it would keep going off after 30 seconds or so. I pulled the alarm and checked to see what would happen if I locked it with no alarm siren attached and it goes into rapid flashing, only stopping when locking again. I attached a new siren but this still happens and no sound. Attached a second replacement siren and this still happens! I did open up the original siren and it did have the battery leak all over the circuitry. So this was definitely at fault at some point. I also checked every fuse related to the alarm and these were fine. (This version of the car has 4 fuse boxes). My code reader also points to problem a problem signal to the alarm siren. Can't for the life of me figure this one out! I did start a thread on this one too.
 

C16RKC

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Must be a very common problem! I have this too!

Never really bothered me that much but I'd always hoped it was a simple fix... I guess not...
 

aycee

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Black CLS350 W218, Blue SLK320 R170, Silver A Class W169
I wonder if it is something as simple as a micro switch somewhere not always closing. The car thinks something is not closed and therefore flashes the lights to tell you. This is certainly the case when I have tried to lock the SLK with the boot not properly shut. Maybe worth lubricating all the switches in the doors, boot and bonnet.
 
OP
Irresistance

Irresistance

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  • Thread Starter
  • Thread starter
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Okay well I have finally been able to get in touch with a local Mercedes electrics wizard so I am hoping to have this looked at sometime this week, early next. Will advise if anything comes of it :)
 

888s

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First of all, Happy New year everyone! I hope 2015 gives you all many miles of trouble free motoring! Any updates since the last post? This problem still occurs for me. At first I thought it may be down to the batteries in the siren needing to charge as it stopped crazy flashing after a while of driving. But now it seems to have started again! How annoying!
 
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C16RKC

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Just a bit of feedback on my own case for the record:

My 2003 S320CDi W220 was blinking rapidly when I tried to lock it and I had to unlock/lock twice to stop the flashing sometimes.

The car has just come back from Alex Crow fixed, it was the Siren which he has replaced and I can report the car now locks/unlocks correctly. Oddly the car now makes a beep each time the indicators flash but this might be an option that can be disabled.

The siren was around £85 + VAT + fitting.
 

888s

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Just a bit of feedback on my own case for the record:

My 2003 S320CDi W220 was blinking rapidly when I tried to lock it and I had to unlock/lock twice to stop the flashing sometimes.

The car has just come back from Alex Crow fixed, it was the Siren which he has replaced and I can report the car now locks/unlocks correctly. Oddly the car now makes a beep each time the indicators flash but this might be an option that can be disabled.

The siren was around £85 + VAT + fitting.

Thanks for the feedback. I've replaced the siren twice with new ones and it still has the flashing problem. Sounds like you got a good deal on your replacement though. 2nd hand off ebay roughly costs the same for the siren alone. Would be interested to know if your replacement was a Mercedes or 3rd party make. If the latter any info on the make would be great! Thanks again.
 

AdamG

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Thanks for the feedback. I've replaced the siren twice with new ones and it still has the flashing problem. Sounds like you got a good deal on your replacement though. 2nd hand off ebay roughly costs the same for the siren alone. Would be interested to know if your replacement was a Mercedes or 3rd party make. If the latter any info on the make would be great! Thanks again.

Thanks from me too for the feedback.

I have also replaced the siren to try and solve the flashing problem but without success.

Maybe I have installed the new siren incorrectly or it needs some additional coding.

Thanks

Adam
 

888s

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Oddly the last ten times I've locked my car it has behaved itself and locked without the crazy flashing! Not sure if I did anything to do this!
 

888s

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Oddly the last ten times I've locked my car it has behaved itself and locked without the crazy flashing! Not sure if I did anything to do this!

Haha! Jinxed it! It came back with a vengeance today! I did notice when locking it a second time the signal lights as we look at the car from the front flashed 3 times but the left indicator flashed one extra time.
 

RingoRingo

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Hello everyone. I have an alarm problem with my 2004 S500L. Recently changed the siren module. I push the lock button on the KG fob, the car locks, light flash 3 times and the alarm should be armed. I leave the key aside, go to the car, pull the driver's door handle and the alarm doesn't start, not the lights nor the sound. On the instrument cluster display it shows "Key not recognized". If I lock the car while inside and the pull the door handle, the alarm starts- sound and lights. Does anyone knows what the problem might be? Thanks in advance. Excuse my English, trying to get it better. PS: tried looking about this exact problem, but haven't found anything, that's why I post here. upload_2020-8-6_9-4-19.gif
 

Naraic

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When you pull the driver's door handle...does the door open? If not...no problem.
 

RingoRingo

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The door doesn't open, but isn't the alarm supposed to start( lights and sound), when someone pulls the handle? It just says "Key not recognized". Before changing the old, bad siren, the lights would start flashing everytime someone touch the car( kids does that), but no sound. I am not sure I understand how this alarm is supposed to work.
 


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