Mercedes Benz repair: Alarm inoperative/1992-300CE, alarm one, 300ce

Question
I know that this problem is outside of your expertise. However I would like to present it to you for consideration. My car alarm is armed and the horn, lights and sounding and flashing. The dealership suggested replacing the Alarm Control Unit. Surprisingly, I unit was left on my seat and I installed it and the same problem occurred. Now I am convince that the new and the old ACU are good and the problem is agraviating. Please help.

Answer
Best guess:
When you install a module, close all doors, hood and trunk, it must be cycled by door key too LOCK then UNLOCK to kill alarm.
One or more of your locks is not reaching the full unlock position.
Your key and/or fob is damaged.
I have personal experience with bad keys on my 1985 300SD.