I am encountering a strange problem with my 2003 C320. This just started today. I drove to my kid's school, stopped the car, got out and locked the doors with the remote. Then the car alarm went off. I noticed that the passenger side front door lock did not lock. So I unlocked the car (the alarm turned off), locked the passenger door manually, locked all other doors using the remote and the alarm went off again. I was in a bit of a hurry so I pressed the unlock button on the remote and went inside. I came out an hour later the alarm was going off again. I pressed the unlock button on the remote the alarm turned off. I drove to work and the same scenario happened. Any help or advice would be greatly appreciated before I contact the dealership. The dealers around here are not the most honest.
Here's what I did. I turned off the Automatic Security in the settings. That seemed to have fixed the alarm problem. The front passenger lock still needs to be locked manually. Last time I had this problem with my ML the dealer was going to charge me $1200 per door to fix the problem. Something about a leak in the vacuum system that lifts and pulls down the locking mechanism. I passed and said I'll use my fingers, they're free If anyone out there has any experience with this issue let me know if this is a DIY or should I just live with it.
Haven't had this problem but before I brought my car in for service my door locks would open when I started driving instead of locking! I wish I would have known how to turn my alarm off ... my car is currently being shipped to NC from NY and the minute the trailor truck took off my alarm started going off. I have a feeling i'm going to get a dead car or my settings are going to be f*cked with.
I am a bit of an expert with alarm problems. I would assume that Mercedes uses the same alarm in most cars and I will give you my experience.
I have had this issue 4 times in three years and have gotten two new alarm horns and one time they said a wire was loose. I have had the alarm go off, the lights just go off, alarm goes off and stops and lights continue to flash. One time dealer replaced the rear SAM unit which did not help but I was told was very expensive. I mention this only so that you do not pay for this and still be stuck with an alarm that is not functioning. The alarm horn does interface with the door lock unit (that is what SA said) so that was why I was having problem with door locking also. The only difference we may have is that my alarm problem would occur several times in a row and then disappear for a few days and then come back. Even though we have different cars you problem sounds exactly like what I was experiencing. One way to live with it, till you can get it fixed, is to lock the other doors from inside with lock switch and then use the little key in the key fob to lock the drivers side door. Sorry to ramble but I wanted to give you all the information I had. Good luck and I hope this helps.
update 06/28/08. Well it's been nearly a week and the problem has not reoccured. One thing I did notice is that when the outside temperature is above 65 F the lock on the passenger front door works fine. Any ideas?
lancelot092466, the reason the alarm went off when you unlocked your doors and walked away is, if you unlock the doors and do nont open one, the doors automatically relock and set the alarm.
Whosdis, Actually I did lock the doors. But the front passenger side door is not working properly and sometimes needs to be lock manually. Happy Belated Canada Day, eh!?
...the passenger side front door lock did not lock. So I unlocked the car (the alarm turned off), locked the passenger door manually, locked all other doors using the remote and the alarm went off again. I was in a bit of a hurry so I pressed the unlock button on the remote and went inside. I came out an hour later the alarm was going off again.
Here you say you pressed the unlock button and went inside. What happens with our cars when the doors are already locked and we press the unlock button without opening a door is, the doors automatically re-lock as if you pushed the lock button, hence the reason the alarm sounded off again.
And thank you for your Canada Day wishes! Happy 4th of July to you!
Alarm problem 
If anyone out there has any experience with this issue let me know if this is a DIY or should I just live with it.
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