Alarm issues on W203

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sinbad

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Jan 21, 2014
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25
Hi all
Wonder if anyone can help?
When locking my 2002 C220 CDI using the key fob the indicators flash 3 times as normal and then proceed to flash quickly until turned off, if I repeat the process 2 or 3 times it will eventually set and be fine, occasionally I come back to it and the indicators are flashing, no alarm noise though!
I have checked all doors etc and they are all shut properly.
HELP!!!
 
You need a new alarm siren, about £100 from the main MB dealer.
You can unplug it as a temporary measure, it could run your car battery down overnight so you might want to disconnect the Negative- side of the car battery for tonight.

The alarm siren has back up batteries inside it so it might still flash the lights even though it has been disconnected.
See... Alarm siren and battery placement - MBWorld.org Forums

Dec
 
Thanks
The alarm did go off a few days ago so I know it works, it's the setting process that seems to be the problem
It's very hit and miss! Would this be the sounder?
Peter
 
The sounder is the siren, the siren is the brains of the alarm system and it usually become faulty when the reach 10 years of age.

If the alarm wasn’t faulty then it wouldn’t be going off immediately after you set it, if a door was open or a door pin switch was defective then the alarm would still set when you lock the car but the hazards would flash two times instead of the usual 3 times.

The fact you have to make several attempts to set the alarm and the fact the hazards are flashing… without the siren sounding… confirms that the siren is defective.
Example… Alarm / Siren Issues : Goes off for no reason/Kills Battery FIX DIY.. - MBWorld.org Forums

Unfortunately its not repairable, the only solution is to replace the siren with a NEW one from an MB dealer or unplug it, if you unplug it then you have no theft protection on your car insurance.

Dec
 
On my Vauxhalls the sounder had onboard soldered NiCd batteries and when they died it was giving grief.

Becuase of the need to use a soldering iron the dealer would only sell the sounder as complete unit, but the batteries were easy to obtain from electronic components stores and it was an easy enough fix as DIY.

Not sure if this applies to MB.
 
On my Vauxhalls the sounder had onboard soldered NiCd batteries and when they died it was giving grief.

Becuase of the need to use a soldering iron the dealer would only sell the sounder as complete unit, but the batteries were easy to obtain from electronic components stores and it was an easy enough fix as DIY.

Not sure if this applies to MB.

it does, and the new batteries are still ni-cad! The problem is the old sirens are so well sealed that attempting to open them damages the casings :(
 
Thanks for all your help guys, prob just going to disconnect it for now, is there an easy to find plug to disconnect it or will I still need to remove the whole thing?
 
See the link in post #2 above and unplug the wires from the back of the siren, put some tape or something to protect the siren plug from wet/damp as the siren plug is live all the time.

The job would be similar to the car in the video below.
How to: Remove a 2001 E320 Mercedes Benz (W210) security alarm siren - YouTube

You can leave the siren in place or remove it, best to remove it so that you can get the part number for when you want to order a replacement in the future.

If you leave the siren attached to the car, but unplugged, it might still misbehave for a day or two as there will still be some charge left in the batteries inside the siren.


Dec
 
Had to replace the siren on my W203 2004 car last year. Initially was the alarm sound was intermittent and then eventually the sound died. After a long time the remote radio (not IR) stopped working and a fuse in the boot (?Rear SAM) would go off. Went online and tracked the issue down to the alarm siren. Got new one from MB and all has been fine since replacement.
 
Ive had similar issues with my alarm going off and it was down to the siren. Battery would drain and lights flashing like crazy with no siren going off. I did exactly as the guys above has described and took out the siren (which is a sealed unit) and ive had no issues with it for a week and counting.

Ive made enquiries at MB and a new siren is just over £100 and is an easy to do yourself with a couple of spanners.
 
Thanks for all your help on this issue, alarm coming out tomorrow!!
 
One other thing, when the car is unlocked, with the remote fob, then the alarm is disarmed, if you unplug the alarm siren while the car is locked then you will be unplugging an alarm that is armed and so it might/should sound off… well it would, if it were not faulty.

Dec
 
Right guys! Had front driver side and passenger side inner wing panels off today trying to find this damn alarm sounder! Can't find it anywhere.
Any ideas? Doing my head in now !
 
Lock the car with the fob, wait one minute or so, then open the driver's door with the emergency key - the sounder should go off for 30 seconds, which should give you ample time to find it?
 
Tried that, the bloody alarm deafened me so much that I couldn't really pinpoint it! Got to say the pic of the location wasn't really what I was expecting!
 
Hope you didn't mind me going on the end of this thread. I have just had a new alarm fitted because the other one seemed to not be working. This seems to not be the case, The new alarm isn't working either. I have tired to set it off and it wont work. Does anyone have any ideas to what I could try next. Thanks
 
What year is the car?
The alarm fuse might be missing, 5amp in boot fuse box perhaps.
Do hazard lights flash when you lock/unlock?

Dec

Edit, what kind of alarm did you get, was it NEW from an MB dealer?

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its a 54 plate.

I have checked fuse 8,9,41. Is there anymore I should know about please.

Yes the hazards do flash. That part seems to be working fine.

It was brought from Mercedes. Brand new. Cost around £93
 
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When the car is locked with the remote there should be a flashing LED light INSIDE THE CABIN to show the alarm is armed, is there a flashing light?
How are you testing the alarm, how are you (trying) setting it off?

Dec
 
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