I think I understood in your explanation that a key fob was used to open or close the doors or unlock the doors or turn off the alarm, regardless, if a key fob was used on the car at all, it would have to be an aftermarket alarm/lock/unlock system that has been installed on the car. The 190e model did not ever come out with a key fob to control locks or the alarm. The important thing to find out now will be how the aftermarket alarm was installed. The system has to be installed to operate the locks via the air pump that locks and unlocks so that the mechanism that does the unlocking and disarming operated properly. If the vac system is activated to unlock the alarm system disarms properly. This is the best way to insure that the deoors dont open prior to the oem alarm being disarmed. A quick and easy way to solve this might be to disconnect the OEM alarm module located in the floor board of the front passenger side. Disconnectiing it should still leave the aftermarket alarm or unlock system in tact. There is a chance that your 190E may not have ever even had an OEM alarm, not all did. IF you dont find the alarm module in the floor board, you likely dont have an OEM alarm and your fault is in the aftermarket unit. Also as a note, I am not sure that the OEM alarm had an ignition disable function. Not sure, didnt think that it did. Second, the arm/disarm trigger for the OEM alarm system is in the door lock mechanisim inside the door lock of the drivers side front door. It is activated and disarmed as the lock is operated by the vacuum diaphram of the central locking system. The locking system needs to be working correctly for the alarm to work properly.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red