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Ice or Frost Build-Up in Sub-Zero Freezer


  • How to manually defrost the freezer section
  • Ice or frost building up inside top area of freezer section
  • Ice on back wall of the freezer
  • What can cause frost in the freezer of a Sub-Zero unit?
  • Freezer shelves, drawers, bins have condensation or fog or are freezing over
  • Freezer basket or drawer rails frozen over
  • Moisture in freezer


  • Freezer door left ajar
  • Freezer drain tube frozen
  • Torn gasket
  • Defrost element failure
  • Ice maker not filling properly


For any frost or ice build-up in a Sub-Zero freezer, follow these steps:

  1. Verify the door was not left ajar for a period of time.
    • Some condensation inside a unit or on the shelving or drawers is normal if the door is opened or left open for a period of time.
    • In warm climates, this will be noticeable more quickly.
    • Keep the door closed, and fogging will resolve on its own.
  2. Remove anything blocking the door from closing.
    • If a drawer could be blocking the door, extend the drawer out fully and close it again. This can help the drawer realign and slide all the way in more easily.
    • If the door does not stay closed after removing obstructions, refer to Sub-Zero Door Difficult to Close.
  3. Inspect door gaskets for tears, rips, or dry rot. Replace if damaged.
  4. Verify the freezer basket retainers are not broken for Classic (formerly Built-In) and 600 Series units.
  5. Clean the Condenser if not done in the last three months.
  6. Check setpoint temperatures for the compartment.
    • On an electronic control panel, the recommended freezer temperature is 0°F.
    • For a dial control, set the dial between 4 and 6. 1 is warmest, and 10 is coldest.
  7. If the drain tube is frozen, clean the drain tube. See:
  8. Defrost the freezer. See Manually Defrost a Sub-Zero for instructions.
  9. Wait 24 hours for the unit to return to normal temperatures and frost to clear after correcting any of the above.
  10. If these troubleshooting steps do not resolve the issue, service is necessary to expertly diagnose and repair the product. Contact Factory Certified Service to schedule an appointment for repair.

Additional Resources

Moisture and Ice

Doors and Drawers



Need further assistance? Contact Customer Care at 800.222.7820 or provide your information below and request a Customer Care representative contact you.

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