Many people assume that a malfunctioning refrigerator is caused by either a bad compressor, or is low on “freon”. Modern refrigerators have very reliable compressors and rarely loose their refrigerant charge. Most failures I see are fan motors, and failure to defrost. Energy saving fan motors don’t last very well and we are stuck with them on Energy Star refrigerators. We save electricity initially, but pay for more frequent repairs. Self defrost refrigerators are much more reliable then before, but a frosted up cooling coil can cause degraded performance and sour milk. Things to look for: Is the light turning off when the door is closed? Is the condenser coil covered with dust or pet hair? Cleaning the condenser once a year is the one thing you can do to lengthen the life of your refrigerator. This is rather easy on Whirlpool products, and tricky on GE.