W202 alarm

cuprastu

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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.
 

gchild

Active Member
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Apr 21, 2004
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507
Car
C280 Sport
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
 
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cuprastu

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Joined
Sep 25, 2009
Messages
38
Location
Herts
Car
W202 230K Sport
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.
 

horgantrevor

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Jan 14, 2011
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w202 c43 & w210 E220 CDI estate w219 W221
hi get the car tested on a star system

also check the wiring to the siren and check for bad earths
 
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cuprastu

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Sep 25, 2009
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Herts
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W202 230K Sport
Never thought about checking for bad earths, that's the quickest and cheapest option to explore first!

Thanks
 

Justin1600

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Dec 28, 2010
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2,079
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C43 AMG
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:
 
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cuprastu

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Sep 25, 2009
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Location
Herts
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W202 230K Sport
What's the PSE pump, is that what operates the central locking etc? If so that is all fine.
 

Justin1600

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Dec 28, 2010
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C43 AMG
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
 
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cuprastu

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Sep 25, 2009
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Location
Herts
Car
W202 230K Sport
Lovely stuff, thanks for your help!
 

andy27168

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Nov 27, 2004
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4,567
Location
Southampton
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1997 C230K, 1999 C43/55 AMG
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.
 

Alex Crow

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Sep 30, 2011
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Super Suffolk
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S210 320cdi
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.
 

andy27168

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1997 C230K, 1999 C43/55 AMG
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.
 
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cuprastu

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Joined
Sep 25, 2009
Messages
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Location
Herts
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W202 230K Sport
This is all sounding expensive! What would happen if I just disconnected the siren?
 
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cuprastu

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Joined
Sep 25, 2009
Messages
38
Location
Herts
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W202 230K Sport
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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