Numerous causes contribute to faulty fridges, but "dying" refrigerators, or appliances that are on their way to the junkyard barring serious attention in the way of replacement parts, can usually attribute their death knells to the compressor or the coils. The compressor compresses gas refrigerants while the coils cool the fridge's insulated interior, both vital processes in the appliance's operation. You can assess the liveliness, or lack thereof, of old refrigerators with a few simple sense-based tests.
Open the refrigerator door and place your hand inside it to feel the temperature. If the interior seems warmer than usual, leave a thermometer in the closed refrigerator for about five minutes.
Read the thermometer. The average temperature of the inside of a working refrigerator is about 40 degree Fahrenheit. Temperatures higher than 7.22 or 10.0 degrees C may indicate a bad evaporator fan, clogged condenser coil, broken drive belt or defective compressor. A clogged condenser coil may be cleaned, but the other symptoms indicate a dying fridge; prevent the fridge from dying by replacing these parts.
Check the temperature in the freezer by hand. If the freezer is cold while the refrigerator is warm, the fridge may have a broken fan blade or dead evaporator fan motor. Without these crucial parts, the refrigerator will soon die.
Note the state of the refrigerator's interior light, if it has one; some older models won't. If the light comes on but the fridge doesn't run, you may have an overheating or defective compressor. This indicates that while some of the refrigerator's secondary functions, such as lights, are operational, its core components may be dead or dying.
Silence any loud noises around the house and listen to your refrigerator running. The regular hum of a healthy fridge is the sound of the compressor. If it starts or stops too quickly or turns on and off erratically, this may indicate that the fridge is at the end of its lifespan. A dying condenser fan, defective compressor or faulty condenser coil may be the culprit.
Listen for a compressor that seems louder than normal. This may be a sign of a loose motor shaft or an unstable compressor flywheel. These can be fixed by an appliance repair technician. However, if the compressor runs nonstop, you probably have a faulty compressor, which could be the fridge's death knell barring replacement.