There are visible indicators such as wear and tear to the gaskets, tears and visibly brittle materials, the gasket dart out of track, or hardened rubber, etc. Other indicators, such as the drawer or door not closing entirely, result in the unit not holding temperature. Or audible indicators such as instant high/low temperature, door-ajar alarms, as well as mechanical cues like persistent humming, clicking, clanking, or hissing – these can indicate compressor or electrical issues to the refrigerator.