Your refrigerator works constantly to keep your perishable foods chilled or frozen. To do this, the unit must complete a cycle of various tasks --- many of which cause a little bit of noise. Refrigerators have several motorised parts that are audible --- sometimes from another room. Determining whether the noise is a problem or not requires some basic troubleshooting. If you're hearing a very loud sound coming from your refrigerator, there could be a problem that requires repair.
Evaporator Fan Motor
One motor that can stir up noise on the refrigerator is the evaporator fan motor. This device is located in the freezer compartment of the unit and is responsible for pushing cold air across the evaporator coils to provide cold air to the rest of the appliance. When the fan comes on there will be an audible whirring sound with normal operation, but a loud sound from the fan motor could mean trouble. You can tell if the sound is coming from the evaporator fan motor if the noise gets considerably louder when you open the freezer door. The motor is located next to the evaporator coils behind the back wall of the freezer compartment. If there is no ice obstruction causing the fan blades to make noise, then the noise is likely from the motor itself, which is malfunctioning. If the motor is bad, have the fan replaced entirely.
Condenser Fan Motor
If the loud noise appears to be coming from behind the refrigerator, its origin is likely the condenser fan. The condenser fan is located near the back of the refrigerator and is often hidden by a removable panel. The noise could be lint and dust build-up causing stress to the fan's operation. If the noise continues once the fan is cleaned, it's probably a malfunction in the fan motor itself. It will need to be replaced.
Defrost Timer Motor
If the loud motor noise is coming from the bottom of the refrigerator, remove the kick plate and see if you can locate the origin of it. If noise is coming from this area it's most likely a problem with the defrost timer motor. This motor controls the timer that tells the defrost heater to turn on and off to keep frost and ice from building up in around the evaporator coils. The electric motor may begin to wear out after considerable use and could become noisy. Replacement is the best solution for this problem.
The least desirable source of your refrigerator's loud noise is a compressor problem. These expensive components are necessary to make the refrigerator cool properly. Repairing or replacing them is required from time to time, however. If the noise you are hearing is a loud clicking noise or a loud hum coming from behind the unit, this could be the source. Additionally, the mounting springs on a compressor sometimes break and when the motor shuts off, the compressor kicks and makes a loud banging sound. In either event, the refrigerator requires significant repairs to fix the issue.