Failures in the Refrigerant Circuit of Domestic Units: Flow Restriction, Compressor Degradation and the Quality of Service Procedures

In domestic refrigerators and freezers, a refrigerant leak, a partial flow restriction and a worn compressor can produce the same complaint of insufficient cooling. Reading only one parameter, such as suction pressure, cabinet temperature or an error code, increases the risk of replacing a serviceable component and of a repeat visit. Published fault detection studies rarely link laboratory fault signatures to field service decisions. The aim of this study is to systematize the differential signatures of flow restriction and compressor degradation in domestic refrigerant circuits and to define service procedures that confirm the diagnosis and preserve the repaired circuit. The study combines a structured review of peer-reviewed research, U.S. regulations and industry standards published from 2020 to 2026 with content analysis of manufacturer service documentation and an analytic single-case study from the author's field practice. The results include a differential signature matrix, a three-domain concordance procedure and a minimum diagnostic record for sealed-system repairs. The findings are of interest to appliance and HVAC-R technicians, service managers, warranty program administrators and instructors.