Which of the following is not an indication of a partial restriction on the high side of the refrigeration system?

The presence of no refrigerant in the system is indeed not an indication of a partial restriction on the high side of the refrigeration system. Instead, a lack of refrigerant typically suggests a different issue, such as a leak or complete loss of charge, which is a more severe problem that prevents the refrigeration system from functioning at all.

In contrast, indications like increased pressures, higher temperature readings, and unusual sounds from the compressor can suggest various issues related to a partial restriction. Increased pressures can occur when the refrigerant cannot properly circulate due to a blockage, causing pressure to build on the high side. Higher temperature readings may also result from this same blockage, indicating that the refrigerant is not absorbing heat properly and therefore is becoming warmer as it fails to function as intended. Unusual sounds from the compressor could indicate that it is working harder than normal due to restricted flow, potentially causing stress or strain on the compressor's components.

Overall, the correct identification of no refrigerant as not being related to a partial restriction helps differentiate between various issues in a refrigeration system, focusing on proper diagnostic techniques.