A receiver is a device to store the refrigerant liquidized by the condenser temporarily, and it supplies the required amount of refrigerant to the evaporator.
A dryer has a desiccant and strainer in itself, and eliminates foreign matter or moisture in the refrigeration cycle.
If moisture is in the refrigeration cycle, parts in it will corrode or freeze inside the expansion valve, which could cause the clogging.
A sight-glass is an inspection hole used to observe the refrigerant flowing inside the refrigeration cycle and to check the level of the refrigerant.
There are 2 types: one is installed at the outlet of the receiver and the other at the piping between the receiver and the expansion valve.
(3) Notes of inspection
Generally, when many bubbles are seen from the sight-glass, it means the amount of refrigerant is insufficient, and when no bubbles are seen, the amount is appropriate.
In the case of no refrigerant or excessive refrigerant, no bubbles are seen, so it is necessary to pay attention. In addition, depending on the conditions such as engine speed or refrigerant pressure, even if the level is appropriate, bubbles can be seen.
For sub-cool type condenser, since more refrigerant is filled at the point at which the bubbles disappear, the refrigerant may be insufficient even if it seems normal in the inspection from the sight-glass.