Troubleshooting a Frozen Evaporator Coil: Finding the Culprits and Solutions

The cooling abilities of a Wine Guardian wine cellar cooling system are remarkable, but every now and then, even the most efficient systems encounter issues. One such problem is a frozen evaporator coil. In this article, we will help you understand the root causes of this issue and how to troubleshoot it.

Why Does an Evaporator Coil Freeze?

The evaporator coil is a critical component in your Wine Guardian system that is responsible for cooling the air before it’s distributed throughout your wine cellar. Several factors can lead to the coil freezing up, impairing its functionality. Let’s delve into the various reasons behind this issue.

1. Air Flow Problems on the Evaporator Side

One of the most common reasons for an evaporator coil freeze-up is inadequate airflow on the evaporator side. This can be due to a variety of factors:

  • Excessive Ductwork: Lengthy ductwork can reduce the air volume reaching the evaporator coil.
  • Dirty Coil: Accumulated dust and debris on the coil’s surface can hinder heat exchange and airflow.
  • Dirty Filter: A clogged or dirty air filter restricts the amount of air entering the system.
  • Incorrectly Sized Ductwork or Grills: If ducts or grills are too small or improperly sized, airflow can be restricted.
  • Blockages in Ductwork: Obstructions in the ducts can limit the flow of air.
  • Weak Fan Motor: A fan motor that’s not functioning optimally won’t move enough air.
  • Short Cycling of Supply Air: Rapid on-off cycling of the supply air can disrupt the temperature balance. If the supply and return vents are too close together, the cold supply air is being pulled back into the return instead of cooling the room.

2. Issues on the Refrigeration Side

Problems related to the refrigeration side of the system can also lead to coil freezing:

  • Low Refrigerant Levels: A refrigerant leak can cause a reduction in refrigerant pressures, leading to freezing.
  • Inlet Air Temperature to Condenser: In cases where the inlet air to the condenser is too cold, the system may not function as expected (this does not apply to spilt systems).
  • Defective Thermal Expansion Valve (TXV): A malfunctioning TXV can impact the refrigerant pressure; too low a pressure can cause freezing.

3. Sensing Issues

Issues related to temperature sensing can also contribute to coil freezing:

  • Incorrect Sensor Placement: Remote controller or sensors located in areas not in the path of airflow won’t provide accurate readings.
  • Incorrect Controller Settings: If the remote controller is mounted outside of the space being cooling and the setting wasn’t changed to only remote the remote sensors, the readings will not be accurate.
  • Heat Gain Through a Wall: Heat gain through a wall can lead to sensor readings that are higher than the actual temperature. Make sure the hole behind the thermostat is insulated and sealed
  • Device Placement Near Doors: Proximity to doors can result in false high-temperature readings.
  • Calibration Needs: Sensors and thermostats might need recalibration.
  • Low Thermostat Set Point: Have a set point no lower than 55°F (13°C) [except on units purchased with the Serving Temperature or All Wine Temperatures Options.]

Troubleshooting Steps

Having reviewed all potential factors contributing to a frozen coil in your Wine Guardian unit, let’s delve into the procedure for diagnosing the problem. This will help you find the root cause of the issue and provide guidance on how to fix it.

  1. Thaw the Unit: Ensure there’s no ice present on the evaporator coil before proceeding, as any ice buildup will restrict airflow and cause the coil to freeze again.
  2. Temperature Check: Verify that the temperature set point is equal to or above 55°F (13°C) and the inlet temperature to the condenser is equal to or above 65°F (18°C) (not applicable to split systems).
  3. Temperature Difference: After the system has run for a few hours, measure the temperature difference between the supply and return air. It should be around a 12-15°F (about 6-8°C) difference.
  4. Compare with Remote Interface: Ensure that the return temperature matches the remote interface temperature.
  5. Diagnose the Issue: The measurements taken in the previous steps will help you diagnose the issue and take action.
    • If your split temperature is higher, the issue is probably air flow related. Investigate potential causes listed in the airflow section above.
    • If your split temperature is lower, measure the split temperature at the unit. You may be gaining heat or losing cooling in the ductwork.
    • If the split temperature is the same, there is probably an issue on the refrigeration side. Refer to the refrigeration section above.
    • If the return is colder than what is being displayed on the thermostat – calibrate the thermostat.


Understanding the reasons behind a frozen evaporator coil and knowing how to troubleshoot the issue can save you from issues in the future. Whether it’s ensuring proper airflow, maintaining refrigerant levels, or accurately calibrating sensors, each step is crucial in maintaining an efficient and reliable wine cellar cooling system. For any additional questions, visit our support page for additional quick help guides and technical resources.

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