The alarm on my 88 300E stayed on today after I opened the door (with the original key). It wouldn't go off even after I locked and unlocked the doors and after I turned the car on and drove home. All the way (about 20 minutes) the car kept honking the horn and flashing the lights. It would stop for a few seconds and then back on again. When I got home I had to disconnect the battery to shut it up. Is there a way to disconnect the alarm and still keep all other functions of the car intact? I heard somewhere about a couple of wires under the passenger's seat carpet. I disconnected those and the alarm didn't stop.
HELP!

The alarm control unit is under the panel in the front portion under the passenger side carpet. You probably disconnected the oxygen sensor. Take off the 2 harnesses and it should stop.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Try to disable alarm by unlocking the passenger side door using the original key (with red dot).

If you want to fix the problem try cleaning he contacts "inside" the lock. It worked for me. If it does not work and you want to use the same key to open all doors, you dealer or may be mercedes shop can get a new lock with a new key. However, it is expensive.
Good luck!
J. Hidalgo

There is a distinct possibility that the lead from the door lock is grounding against the sheetmetal of the door. I had this happen on my 89 300e. It was on the passenger side. My alarm was always going off. I tried everything, even disconnected the alarm horn (didn't stop the lights from flashing). Found the problem quite by accident. Had the passenger side door panel off to check the connector on the seat adjustor switch. Noticed this single lead coming through a punched out hole near the door lock. It was frayed. At the time, I didn't know what it was for other than the fact that it was connected to the door lock. Taped it up, and found that my problem was solved. Go figure??

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Jeff L
1987 300e
1989 300e
1987 BMW 325

It is possible that something is wrong on the passenger side door. However I can't get to it (previous post) :)
What I need to know is exactly where under the passenger carpet. I lifted it up and saw two cables which I disconnected but it wouldn't go off. Even today after the battery had been disconnected, I connected it again and off went the alarm. I did see a panel under the passenger's carpet towards the firewall. Taking off the plastic panel I saw a red box and some other stuff. Is the alarm there? Sorry to keep rambling on but I'm just lost when it comes to this car. Any help is greatly appreciated.