Refrigerator: Why isn't my refrigerator cooling well?

The refrigerator defrost sensor-also known as the defrost bi-metal termination thermostat-trips when it detects that the temperature of the evaporator is getting hot enough that it might overheat. When the defrost sensor trips, it shut off power to the defrost heater. If the defrost sensor trips because it's not working correctly, frost builds up on the evaporator fins, eventually making the refrigerator and freezer not cool well. You can use volt/ohm meter to check the defrost sensor for continuity. Replace the defrost sensor if it shows no continuity at around 0 degrees F.

The diffuser--or air damper--in a refrigerator controls cold-air flow from the freezer compartment to the refrigerator compartment. If the diffuser is stuck fully open, food in the refrigerator freezes. If it's stuck closed, the refrigerator becomes too warm while the freezer cools properly. Replace the damper if it's not controlling the flow of cold air from the freezer.

If the refrigerator is not cooling enough, the thermistor might be faulty. The thermistor sends temperature information to the thermostat, so a broken thermistor will give bad information.

Dust-covered refrigerator coils can prevent the refrigerator and freezer from running efficiently and cooling properly. Follow the instructions in your owner's manual for cleaning the condenser coils. Unplug the refrigerator before accessing and cleaning the coils. On most refrigerators, the coils are behind the bottom front grill. Clean the condenser coils with a coil brush.

The refrigerator automatic defrost system periodically melts frost from the evaporator to improve heat exchange. During defrosting, the compressor stops, the defrost heating element turns on, and frost melts from the evaporator fins. The condensate drips to a evaporator drip tray below the evaporator and then flows through a defrost drain tube to a drain pan next to the compressor in the machine compartment. The condensate water evaporates from the drain pan before the next defrost cycled. If the defrost process fails, diagnose and repair the problem.

The evaporator fan is mounted on the evaporator assembly. It moves air across the evaporator fins and through the cabinet for cooling. If the evaporator fan is defective, replace it.

The defrost timer is an electro-mechanical device that controls the intervals between automatic defrost cycles in the refrigerator. The defrost timer motor runs and moves the control components in the device. When the control contacts in the defrost timer advance into the defrost cycle, the compressor stops and the defrost heater turns on for a specified period of time to melt frost off of the evaporator fins. This promotes more efficient exchange of heat across the evaporator. When the specified period of defrost ends, the defrost timer contacts switch back to allow normal cooling operation in the refrigerator.

You'll need to replace the defrost timer if it doesn't advance when activated.

Faulty contacts in the timer can also cause the defrost heater to either not energize at all or constantly energize. In that instance, replace the defrost timer.

The refrigerator or freezer doors swing on hinges that can be damaged or bent. Over time, the doors may begin to sag, allowing warm moist air into the refrigerator or freezer door that creates excessive frost that can eventually cause the drain tube to freeze. This refrigerator repair involves adjusting or repairing the hinges so that the doors work properly and stay aligned.