The alarm light is flashing, the freezer seem to be working,

A flashing red light on a tall freezer indicates that the appliance has detected a temperature alarm, and the temperature inside the freezer has likely dropped below the desired range. A temperature of -6 degrees Celsius is much lower than the recommended temperature for a freezer (-18 degrees Celsius), which can cause frozen food to become damaged or spoiled.
To resolve the issue, you should first check the freezer's manual for troubleshooting tips and recommended actions. In general, you may need to adjust the thermostat to a higher temperature, remove any obstructions to airflow, or defrost the freezer if ice buildup is blocking the evaporator coils. If the issue persists, you should contact a qualified technician to diagnose and repair the freezer.

Check along the back and sides of the freezer for any vent-like openings that are covered or blocked by packages. There may be a sensor that's not getting air flow as it should. Although most upright freezers are now frost free, there still can be ice buildup in critical areas such as the thermal sensor or the fan. Can you tell if the fan is running?

Even if the compressor has failed, your frozen items will keep the temp down for several days. I suggest you move the frozen goods to a neighbor immediately. Meat or fish in particular quickly becomes unsafe to eat without at least refrigeration.

Warning light (red)
If the temperature warning light (4) lights up, it
indicates that the temperature within the freezer has
reached a level where the safe food storage is no
longer ensured. When the freezer is first switched on, the warning light will stay on until the temperature has dropped to
a safe level for the storage of frozen food.

Temperature acoustic alarm
This appliance incorporates an alarm which gives off
an audible signal whenever the warning light comes
on. This signal can be temporarily stopped by
depressing the push button for fast-freezing (6).
The fast-freezing push button can be released as
soon as the warning light is off.

Open door acoustic alarm
This appliance also incorporates an alarm which
sounds if the door is left open for more than 60
seconds. The signal will be stopped when the door is
closed again.

Dado

Because it does not achieve the correct temperature (for example: -18 degrees centigrade).
For a more precise answer I need more information.
A lot of things may be incorrect:
- Doesn't work defrosting cycle
- The cooling fan is not working
- Too much ice on the evaporator battery
- Faulty thermostat or NTC sensor
- Faulty cooling system (gas leak)
- Compressor
- Electronic

Dado

Red Alarm Indicator Light
Under normal operating conditions, the internal temperature of the freezer will ensure the long-term conservation of the stored food. When such temperature rises above a certain level (-12 °C), the appliance will trigger an acoustic and light alarm. The light alarm is a blink red light (Red Alarm Indicator Light), while the acoustic alarm is an intermittent sound.
You can stop the acoustic alarm by pressing the Acoustic Signal Stop Switch once.

When switching on the freezer for the first time, the Red Alarm Indicator Light will blink until the internal temperature has reached a level required for the safe conservation of frozen food.

Fast Freeze function
If more than 3-4 kg of food is to be frozen:
1. Press the Fast Freeze Switch for 2-3 seconds to activate the fast-freeze function 6-24 hours before placing the fresh food in the freezer, the Yellow Fast Freeze Indicator Light will illuminate. The compressor will now run continuously, to ensure that the fresh food is frozen as quickly as possible.
2. It is possible to deactivate the function at any time by pressing the Fast Freeze Switch for 2-3 seconds.
3. Place the foods in the freezing compartments (indicated with graphics).
4. Once the food is completely frozen (it may take up to 24 hours) you can manually switch off the fastfreeze function by pressing the Fast Freeze Switch for 2- 3 seconds and the Yellow Fast Freeze Indicator light will also go out.
5. Move frozen food from the freezing compartments into the other compartments (storing compartments) to make room for another freezing.

If the Fast Freeze Switch is accidentally left on, the fast-freeze function will be automatically switched off 48 hours later. The Yellow Fast Freeze Indicator light will also go out.

I believe that you all understand. If you intend to freeze larger amount of food then certainly a few hours before some shopping switch on the fast freeze function.

Dado

This is normal. All commercfial freezers must defrost 3 to 5 times a day, or they will freeze over at the coil and then stop freezing. A timer in your freezer turns off the compressor and turns a heating element on for 10 to 15 minutes. During that time the coil heats and melts frost from the coil. Usually within 30 minutes the temperature will briefly rise to 20 t0 25 degrees F and then quickly drop down to 0 degrees F. The food rarely defrosts in this short period of time..

alarm should go off when freezer reaches minus 18c or lower.

You need to check the temp in the freezer to make sure it's down to around 10 degrees. The alarm will go off much above that.

that's the same problem i incurred, i replaced the thermostat and the fan. seems to be working fine.

What is the temp in the freezer, sounds like temp is to low..no water should be coming out of freezer, sounds like may be defrosting Need to check the temp to make sure its cold enough.. thats what that alarm is for