Alarm going off
 

I have a 1992 300D 2.5 and the alarm went off at 3am for no reason, turned it off. Wife told me that now the door locks do not work now, push the lock button on key fob and some times the alarm goes off and the doors do not lock. I tryed to lock the doors with the key and only the drivers door locks. What is going on?

Answer
 

Factory Alarm System Issues
http://www.peachparts.com/shopforum/diesel-discussion/150748-factory-alarm-system-issues.html#post1143583

Why would the door locks stop working?

door locks are tied to the alarm system, if there's a fault in the alarm system then its possible that the default setting would be to disable the locks. it's all a guess though

If I unplug the alarm will the locks work again?

try it, easy to do and find out.

when was the last time a car alarm actually helped? I mean, really, if somebody wants your car it's theirs.

If there is something sitting on a seat they want, it's theirs... takes about 5 seconds to break a window and grab the item. Your alarm won't even go off.

I disconnected and/or removed all alarm parts from the car that were easy to get at... and I don't leave anything valuable in the car.

Well, I looked under the mats on the passenger side floorboard and the only thing there was the connection for the airbag. Where is my alarm control box at?

Answer
 

Look at the pictures in this thread..
* Remove floor mats.
* Look at the bulkhead/firewall.
* Remove large black steel panel.

How-to: Disable alarm on a 1993+ W124
http://www.peachparts.com/shopforum/tech-help/269799-how-disable-alarm-1993-w124.html#post2386200

I did and there is nothing like that there, the only thing that is there is one red plug and that is for the airbag. What next? And now I cant open my fuel door, it is locked and will not open. How do I open that also? Thanks

Answer
 

Look behind the passenger kick panel...

I did and there is nothing there.

I think my 93 parts car has alarm goodies stuffed behind the ash tray.
it's also possible an aftermarket alarm kit was installed in your car... pop the hood and look for foreign items near the fusebox. any large horns or anything added to the car?

Thanks for all the help, the problem was the vacuum pump under the back seat. One of the solder joints broke so I resoldered the joint and all works now.

Well the alarm is not working right now, I got a vacuum pump from a 190E. The door locks work now but the alarm still goes off when you open the back doors. Yes there is a horn under the hood, does that mean the alarm is a aftermarket?

Factory alarm uses standard Bosch or Hella horn on driver side fender near ABS module.

The alarm module is located under the carpet, on passenger side front floor board.