Final answer:
The cooler line on the receiver drier is caused by a restriction in the receiver drier.
Step-by-step explanation:
The technician notices that one line on the receiver drier is cooler than the other. This is caused by a restriction in the receiver drier.
The receiver drier is an important component in a refrigeration system. It is responsible for removing any moisture and contaminants from the refrigerant. If there is a restriction in the receiver drier, it can disrupt the flow of refrigerant and cause one line to be cooler than the other.
It is important to address this issue by replacing the restricted receiver drier to ensure proper functioning of the refrigeration system.