W202 alarm

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cuprastu

Member
Joined
Sep 25, 2009
Messages
38
Location
Herts
Car
W202 230K Sport
I have a problem with the alarm on my car, it is a facelift 202 and will randomly go off, so have resorted to turning off the interior sensors everytime I park it at night, mostly this is ok. However the other day I noticed that the indicators on it were flashing really fast but no siren going off, once I unlocked it it was ok again.

Is there anything I can check, or a battery in the alarm i can replace that might sort this out? The cars main battery was changed last winter so don't think it's a battery voltage issue.
 
I had a similar issue. Turned out to be a cricket that got in some how triggering the interior sensor. Took a few weeks for it to surface, had the interios sensor off in the meantime
 
Mine has been doing it ever since I have had the car, which is over 2 years now so anything living should be well dead! It's just annoying and seems to be getting getting worse. It's the rapid flashing of the indicators the other day that started me worrying about it more.
 
hi get the car tested on a star system

also check the wiring to the siren and check for bad earths
 
Never thought about checking for bad earths, that's the quickest and cheapest option to explore first!

Thanks
 
Try cleaning the interior sensors on the B pillars first, if that still does not cure it then the chances are the PSE pump is at fault.
But as said above check the wiring to the Siren for corrosion :thumb:
 
What's the PSE pump, is that what operates the central locking etc? If so that is all fine.
 
What's the PSE pump, is that what operates the central locking etc? If so that is all fine.


Yes mate, it is in the boot on the drivers side. Do the things i said first, if it still goes off then you will need to do a Star short test. If there are lots of fault codes stored in PSE which say Left protection senor & Right protection sensor, then the PSE pump will probably be faulty :thumb:

The central locking etc will still work mate
 
Lovely stuff, thanks for your help!
 
False alarms like this (once false alarms have been eliminated) are most likely caused by a faulty alarm siren, the back up battery in the siren gives up causing the issue, I had this exact issue with my C43.
 
Andy above has it right, if the alarm goes off without the siren (indicators flashing), it is usually the siren at fault.

This will be mounted in front of the N/S/F wheel, and can be disconnected to prove the fault.
 
Hi,
The Siren battery cannot be replaced, you have to replace the entire Siren, approx. £75 from MB only.
You will need a T30 security Torx bit to remove it from the car.
 
This is all sounding expensive! What would happen if I just disconnected the siren?
 
Well if it fixes the fault I might just leave it permanently disconnected. Don't need a poxy alarm anyway, no one takes any notice of them!

Thanks for your help.
 

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