K3504 partly working


I am trying this forum with a hope for a hint.
I have recently bought and assembled a Voltage Drop Car Alarm K3504.

I have checked the circuitry and I cant find any faults.
The components seems to e in the correct position and there are no cold solderings.

When turned on, it does not work properly.

The LED indicator turns on, but does not blink. (Capacitor??)
When the voltage drops, the alarm starts almost immediately and the variable resistors does not seem to have any effect.

The buzzer never sounds, but I know that the buzzer is OK.

Any hints appreciated :slight_smile:

Any hints would be appreciated. :slight_smile: