Alarm problem solved.

You can NOT install a remote entry unit in all W124 models as shown elsewhere in this forum.

Only if your car has exactly the same wiring configurations should that method be used, and even then you must test the factory alarm to ensure that it works properly with the remote as well as the key.

When installing the remote control module, you MUST cut the lock/unlock wire going to the vacuum pump that also signals the arm/disarm wire going to the anti theft alarm control unit to arm and disarm, connect the wiring in series at the cut wire.

If you use the wrong wire, remote locking and unlocking will have no affect on the alarm. For example if you lock the car using the key, or the passenger door lock button, then later unlock the car using the remote, the alarm will be activated and you can only stop it by using the key to unlock/disarm.

Also if you lock the car using the remote, if it’s not properly wired, the alarm system will not arm, so it’s useless.

I shudder at the thought of how many W124 models (and others) are out there with botched alarm systems for this and other reasons.

Forget the "blue wire" unless you have two of them.
Acky