Hello all, I'm new to the forum. I purchased a 2007 c280 4matic for my daughter some time ago. She is now having a problem with the siren and the lights going off. Now doing a little research on it, I have disconnected the siren under the wheel well and now the lights are still going off. I had the battery tested and it was fine as well as the battery connections. Any help would be appreciated.

 

I have pulled the plug on the siren hoping it was just that, but noticed the lights are still flashing from time to time.

 

Which battery did you have tested? The main car battery or the secondary one that powers the alarm system and is frequently the cause of the problem you report?

 

The main battery under the cabin filter. Excuse my ignorence, where would the secondary battery be.

 

The alarm system has its own battery in the wheel well, and if I remember correctly, it is integrated into the siren itself. Had this problem with my 2003 and the whole thing needed to be replaced. Had it done at a dealer so unfortunately I don't have any details about removal or replacement.

 

Thanks again for taking the time to reply, but I have disconnected the plug from the siren in the wheel well and the fog and rear lights are still going off indicating an alarm. My question is if I replace the siren is there not something else telling the alarm to engage. Thanks again for any help.

 

Is there just the siren or is there an alarm module as well? I thought it was all one unit. Plus, I remember the SA saying it had its own power supply as back up so that a thief couldn't disable the alarm by disconnecting the main battery.

 

Thats the thing I'm trying to find out, I dont mind spending the $200 for a new siren but I want to make sure there isnt a modual or something engaging it thats damaged.

 

Take a look at bayhas.com. Check the electrical section and you will find plenty of info on the anti-theft alarm. Also, search this forum for "anti theft alarm". Plenty of info there too. Good luck.

 

This is the correct link to the site I mentioned:

http://bayhas.com/mercedes/w203/contents/home.htm