Common Sub-Zero Refrigerator Error Codes & What They Mean

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While there are few malfunctions in Sub-Zero refrigerators, their error codes are helpful in troubleshooting the occasional issue. What is one of the most common Sub-Zero refrigerator error codes? Error code EC24 indicates a defrost system problem. Try cleaning the condenser coils to restore proper function. Explore more common codes and their meanings to decipher and solve Sub-Zero refrigerator problems.

Making Sense of Sub-Zero Refrigerator Error Codes

Each Sub-Zero refrigerator error code corresponds to a specific issue. Knowing what the code means can narrow down the problem and help determine if a minor adjustment or professional repair is necessary.

Sub-Zero Refrigerator Error Code EC06

Problem: The refrigerator thermistor is giving repeatedly inconsistent readings, with temperatures that are too high or too low. Since this is one of the most common Sub-Zero refrigerator error codes, it may also flash if the thermistor shorted for more than 10 seconds or read open. 

Cause: A SubZero error code of ECO6 is likely due to a thermistor malfunction, leaving it unable to accurately measure the internal temperature. A thermistor read open is not receiving any electrical current and likely requires replacement. Sub-Zero recommends that only a professional repair service troubleshoot this particular code.

Sub-Zero refrigerator error codes
Image Credit: Sub-Zero

Sub-Zero Refrigerator Error Code EC20

Problem: There is a freezer defrost system terminator issue, preventing the defrost system from starting or stopping. One of the more unique Sub-Zero refrigerator features is separate evaporator and condenser systems for the refrigerator and freezer. This means that a malfunction in one system should not affect the other.

Cause: One of the defrost system’s wires isn’t receiving any voltage, preventing the start or stop of the defrost cycle. If the defrost cycle doesn’t stop, you’ll find your refrigerator runs constantly, risking a condenser malfunction and increasing energy usage. Sub-Zero recommends that only a professional repair service address this code as well.

Sub-Zero Refrigerator Error Code EC24

Problem: Defrost underheat. This means the defrost system is not providing enough heat to melt frost on the evaporator or condenser coils. If frost accumulates, the coils may not cool refrigerant properly, leading to higher internal temperatures.

Cause: Dirty condenser coils can make the defrost system work harder to melt accumulated frost. If the refrigerator’s temperature is only slightly higher, try cleaning the condenser coils. 

The Sub-Zero clean condenser coil process includes these steps:

  • Turn off the refrigerator’s power at the control panel.
  • Lift the upper grille to access the coils
  • Vacuum the coils in a vertical motion with a narrow hose attachment.
  • Pull down the grille.
  • Restore power at the control panel.

If this doesn’t clear the code and refrigerator temps are significantly higher than normal, schedule a professional repair.

Sub-Zero Refrigerator Error Code EC40

Problem: The freezer compressor is running excessively. In addition to error code EC40 you may also see a Sub-Zero flashing service light.

Cause: The freezer door may have been left open or the condenser coils need to be cleaned. Close the door and/or clean the condenser coils. Wondering how to reset a Sub-Zero refrigerator error code of EC40? Press and hold the control panel’s door ajar alarm key for 15 seconds. If the door wasn’t open, the coils are clean and the internal temperature is significantly high, call a professional service.

Sub-Zero Refrigerator Error Code EC50

Problem: The refrigerator compressor is running excessively. A flashing “Service” light may accompany this code as well.


  • Refrigerator door is ajar: Close the door and press and hold the door alarm ajar button for 15 seconds to clear the code.
  • Dirty condenser coils: If the temperature is near normal, clean the coils and clear the code by pressing the door ajar alarm button for 15 seconds.
  • Grille or kick plate is blocked or enclosed: Make sure nothing is obstructing the grille or kickplate. Obstructions can cause sealed system failures that require a professional repair.

If refrigerator temperatures are significantly higher, refrain from troubleshooting and contact a professional repair service.

The experts at Tiger Mechanical can perform any Gilbert Sub-Zero refrigerator repair. Call us to resolve Sub-Zero refrigerator error codes or any other malfunction.

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