W221 Alarm Siren - A2198203226

[Mogul]

I removed my alarm siren last year when it started going off for no apparent reason at circa 10yrs old.

I may sell the car this year so was thinking I should put one back on.

What’s the best option?

A used one might do the job, but…

A few ‘new’ ones I have seen listed online appear to be NOS (New Old Stock) and some will have been on the shelf for 10 years already.

I’m surprised there isn’t more of a ready market for aftermarket alarm sirens as they will probably all fail at some point..

[cjb44]

You will be extremely lucky if the siren is the problem, usually it will be the main alarm box or a sensor for a door etc.
Good luck

[Mogul]

Does this come from personal / painful experience?

I ask because there is mucho ‘evidence’ on the ‘net about the small batteries within these alarm siren units which can and do fail.

On my car, if I disabled the tow-away sensor (which was otherwise functioning i.e., it would go off if I jacked up a corner) the alarm wouldn’t go off randomly.

[cjb44]

I am afraid my experience was with an Audi TT which cost me £1,000 to replace the main unit which had succumbed to damp/ rust although the car was dry, caused by alternate warmth and cold over the years. I was not aware that the sirens had a battery fitted. I have owned several Mercedes but fortunately they behaved themselves. I did have trouble with a rover 75 connoisseur but that was due to bonnet sensor which defied all attempts to correct, no adjustment changed anything neither did a new sensor switch.

Edited by cjb44 on Sunday 18th February 19:53

[KillerHERTZ]

It will almost certainly be the battery within the alarm module, common issue on Mercs of this age.

The unit will be about £160 and available from MB, it is located behind the front passenger wheel arch liner and you will need a torx security bit to remove the old one.

Takes about an hour to do the job.