Suddenly, the compressor of my Dometic CFX 50 refrigerator in my Mercedes 508D was running continuously, even though the cooling compartment was extremely cold. To my surprise, the temperature displayed on the screen was 43 degrees Celsius, indicating a possible thermostat malfunction.
I was able to find a replacement thermostat in an online shop for a few euros and replaced it using the following steps:
First, I removed the 14 screws holding the vent on both sides (3 on each side),
and the (8) bottom,
to carefully open the vent.
In order to remove the two screws holding the thermostat wire, I had to remove the compressor control module and its cover by loosening the screws holding the cover,
and the screw behind the module holding it.
After pushing the compressor control module aside, I was able to remove the screws holding the thermostat wire,
and could carefully pull the thermostat out of place.
In order to disconnect the thermostat from the main PCB, I had to remove its cover by loosing the screws holding it.
Then the screws holding the main PCB could be loosened,
to finally disconnect and remove the thermostat.
Unfortunately, the connectors of the new thermostat didn’t match with the connectors of the old one.
So, I simply soldered the connection of the old thermostat to the new one.
After stripping the wires, I attached the new thermostat to the main PCB and reassembled everything in reverse order.
The screen displayed the correct temperature and the refrigerator was working again. 
