I just bought a used ML320 from a MB dealer 2 months ago. This was a single owner car with 53k miles and in excellent condition. All maintenance was performed by MB. Occasionally, (usually at about 2:00 A.M.) the alarm goes off and sooner or later, my neighbors will complain. Any suggestions for solving the issue will be appreciated. Best guess is I may need to replace the alarm module but I would not mind disabling the alarm. Also, will turning off the Tow switch deactivate the alarm?
Thanks!

As you exit the car try de-activating the "tow" sensor by depressing the switch that looks a fishing hook.

IF that doesn't work find a dealer that will turn off the alarm.

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Ironically I bought a 2001 ML320 from a MB dealer with 63k miles on it and have the exact same problem. I ended up disconnecting the alarm horn which kills the sound that woke up the neighborhood. I am still seeing the lights blink, which seems to happen even more frequently now. Almost everytime after I lock the car the alarm goes off.

Did you ever figure out what caused your problem?

I'm having exactly the same problem on my 2001 ML320. Can you please tell me how did you deactivated the alarm horn? I took out its fuse but it is still running and the neighbors are really unhappy. Thanks.