Refrigerator: Why won't my refrigerator cool at all?

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.

The condenser fan is in the machine compartment of the refrigerator next to the compressor. It moves air across the condenser coils to help cool the hot refrigerant coming out of the compressor. The refrigerant is cooled before it moves through the expansion device and into the evaporator. If the condenser fan is defective, replace it.

The electronic control board-also called the main control board or the power control board (PCB)-controls the compressor and the defrost cycle. When it senses that the compressor must run to keep the refrigerator cool, it sends voltage to the compressor and fans. The electronic control board also receives signals from temperature sensors to monitor the temperatures inside the refrigerator and freezer. With this information, the electronic control board controls the defrost cycle. You can usually do a diagnostic test on the electronic control board to see how well it's working. The test varies by model, but the most common is the Forced Defrost test. See the tech sheet for instructions on running the diagnostics. Replace the electronic control board if it's not working correctly.

The start relay—also called the PTC relay—is the electrical device that jump starts the compressor motor. The compressor motor won’t start without the extra starting current from the start relay.

If the start relay isn’t working, you’ll often hear the compressor clicking and humming briefly every few minutes. To verify that the problem is the start relay, unplug the refrigerator, remove the start relay and shake it. If the start relay rattles, replace the start relay.

The temperature control board-also called the electronic control board-is in the machine compartment next to the compressor, behind a panel on the back of the refrigerator. The temperature control board controls the compressor and other major components in the refrigerator. You can test it using the diagnostic test procedures provided in the tech sheet for the refrigerator. Replace the temperature control board if it doesn't work at all or isn't controlling the components correctly.

The temperature control thermostat is also called the cold control or cold control thermostat, and is located in the control housing. The thermostat has a sensor tube attached to it that detects the temperature inside the refrigerator cabinet. The temperature control thermostat controls the temperature inside the cabinet by turning on and shutting off the compressor based on the temperature sensed by the sensor tube. Replace the temperature control thermostat if it fails to sense temperature properly or if it does not cycle the compressor properly.

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.

Repairing the compressor in the refrigerator usually involves the replacement of the start device and/or overload on the motor. If the compressor looks to be in working order but will not start, then replace the start device and/or overload. If the compressor is locked up, or it runs but will not compress the refrigerant, then replace the compressor. A refrigerator service technician will need to complete this repair since it involves the recovery and recharge of the refrigerant.