Ok..so I have searched multiple sites and multiple forums for this exact problem and I can't find anything...some similar problems but nothing like this.

So I noticed that the siren doesn't BLARE when the alarm is tripped (I opened a door from the inside), just the lights flash. So ok...I assume then that the siren needs to be replaced, so I remove it behind the right passenger wheel well and noticed that it and the connector are pretty scummy so I clean it up and plug it back in to see if that had anything to do with it. So then I go to test the alarm again (opening door from inside) and BAM..Ear Piercing siren is wailing in my ear..I then press the unlock button on the key to make it stop. So I proceed to lock the car again..wait 10 seconds...and open the car door again from the inside..........and no siren, the lights are doing the rapid flashing but there is no siren at all. I have come to the conclusion that once unplugged and plugged back in, the siren will only sound once the next time the alarm is tripped and won't work any other time. I am trying to figure out if this is indeed the siren or something else in the alarm system like a relay or something....Can someone please give any advice they may have. It would be greatly appreciated.
Thanks
Jason

2001 C320

I am not sure if my car ('05 c230) and yours have the same alarm, but I have had several issues with mine. Each time I take it to the dealer they fix it and it just stops working after 3 - 4 months. It has had a couple horns put in and it just acts up again after a few months.

I would say a need siren should help. I have not looked at mine, but I suspect that it's location is leading to it getting dirty and wet. Maybe if you could seal it up after you put in a new horn that may help. I have heard that they are around the $100 price range.

This post is not very helpful, but at least a start.

I removed and disassembled the siren and found it to be heavily corroded on the inside. The actual siren casing was cracked from the over tightened bolt that held it on the bracket, which is how the water came in. The battery in the siren was completely dead and the circuit board has blown circuits on it. I am leaning more towards a faulty siren but want to make sure before I dump $160 at Portland Mercedes.

so i got a new siren ($165 from Portland Mercedes) and that was indeed the problem..and I even gained the chirping feature!! Bonus!!

Do you know the part number?

On the receipt they gave me it is 215-826-02-90. When I called Portland Mercedes I just asked for the alarm siren for an 01 C320. I didnt mention a part number.

thanks, but that part number is a lens:

http://www.worldimpex.com/parts/merc...ns_802003.html

Sorry..bought both at the same time and looked at the wrong spot. The siren number is:

219-820-32-26

wow; surprisingly it's $200 at Duval, which usually has the lowest prices on parts; the only online place I found beats them at $150

http://www.worldimpex.com/parts/merc...en_928127.html

wow is right! Duval? I haven't heard of it. Do they have a website?