When you purchase a Nor cold cooling unit you expect it to last for a long time but all mechanical devices have a limited life and will eventually wear out. If you see yellow residue behind your refrigerator or a strong ammonia smell this indicates that the cooling unit has failed and needs to be replaced.
Dometic & Norcold absorption fridges use the process of distillation, the working fluid (ammonia) is separated from the water in the fridge using heat. The electric heating elements or LP gas flame drive this distillation process in the boiler of the fridge. The boiling of the ammonia converts it into vapor that is then pumped through the system of tubes to the frige where the heat converts the vapor back into liquid that cools the refrigerator.
The problem is that when the boiler temperatures rise to unsafe levels the cooling unit can be damaged. The Fridge Defend monitors the cooling units boiler temperature and warns you of any unsafe conditions.
When the Dometic or Norcold factory builds these fridges they apply expanding foam on the back of the refrigerator to seal and secure the cooling unit. This insulation is necessary to prevent heat from getting into the refrigerator cabinet where it can cause corrosion of the refrigerator and freezer components. When the fridge is shipped to the RV manufacturer they may or may not install this insulation. If they do the assemblers will often misapply this foam leaving air and moisture trapped in the area of the refrigerator where it is installed. This can cause a host of refrigeration problems and is the primary reason for many of these refrigerator failures. Nor cold cooling units