IOWN A 2003 C-230 COUPE AND FOR THE LAST MONTH MY ALARM ACTIVATES BY ITSELF BOTH WITH THE VEHICLE PARKED AND WHILE DRIVING IT HAS PROGRESSED TO WHERE I CAN'T DISARM IT AT TIMES ALSO WHEN I ARM IT THERE IS A FAINT BEEP THAT SEEMS TO BE COMING FROM THE FRONT PASSENGER WHEEL AREA IT BEEPS FOR AROUND 3 MINUTES DOES ANY KNOW THE COST OF REPLACING THE ALARM SYSTEM ? OR WHAT THE PROBLEM COULD BE

 

I had a similar problem with my 2003 C240the alarm would go off randomly (when parked) so i had to manually lock the doors and not activate the alarm. One day at work, this weird sound started coming from the front passenger sideit turns out it was the actual "horn" that makes the alarm sound. I called the dealership so they could hear the noise and all the could say was to bring it in so they could look at itand charge me $200 to do that! Luckily, where i work we have a mechanic shop, so the guys put it on a lift (the sound wouldn't stop) and removed the bottom panel, and right behind the front passenger wheel is where they found the horn hooked up to 2 wires. they disconnected the horn and to this day i have it in my trunki'm not sure if i'll ever replace it...

Hope this helps...it may just "beep" now, but trust me, when the thing starts this awful noise, you'll want to know what to rip out!