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Sub-Zero Refrigerator Freezer Not Defrosting? This May Be Why…

Sub Zero defrost problem

Though we want our freezer to keep food frozen, a buildup of frost isn’t a good sign. Even Sub-Zero refrigerator freezers can fall victim to this problem, prompting the question, “Why is my freezer not defrosting properly?” It could be that the freezer door was left open, allowing humidity to enter and form frost. Determine the most likely reasons for a Sub-Zero refrigerator freezer not defrosting with these troubleshooting tips.

Figuring Out Freezer Frost: What to Do for a Sub-Zero Refrigerator Freezer Not Defrosting

While a Sub-Zero refrigerator freezer not defrosting may have malfunctioned, often a minor adjustment or simple repair can solve the problem. Learn how to diagnose and resolve common causes for defrosting issues to restore freezer function.

Too Few or Too Many Items

Have you found that your Sub-Zero refrigerator is warm when there are too few or too many items? The right amount of food in a freezer is also essential to maintaining its temperature. Too few items can overwork the compressor, causing a rise in temperature that forms frost. Meanwhile, too many frozen foods can block airflow, also resulting in frost.

To limit ice buildup in Sub-Zero freezer, aim to keep it ¾ of the way stocked. This will help maintain consistently cold temperatures without limiting airflow.

Freezer Door Left Ajar

An open freezer door is one of the most common reasons for a Sub-Zero refrigerator freezer not defrosting. If the freezer door is left ajar even a little bit, the warm, humid air that enters will collect and form frost. When using the freezer, always make sure the door closes completely and is left open for as little time as possible.

Sub-Zero refrigerator freezer not defrosting

Torn Gasket

The rubber gasket around the freezer door’s perimeter creates a tight seal when the door is closed, keeping cold air in and prohibiting warm air from entering. If the gasket is dirty, torn or rotted, the seal can be compromised, allowing warm air to enter and form frost. 

While a dirty gasket can be cleaned with a damp cloth, a damaged gasket must be replaced.

Freezer Drain Tube Frozen

If your freezer is properly stocked and the door is closed and sealed, a frozen drain tube could cause a Sub-Zero defrost problem. Excess freezer condensation passes through this tube to the drain pan underneath the refrigerator, where it evaporates. However, sometimes ice buildup can block water flow through the tube, leaving excess condensation to form frost.

A Sub-Zero freezer drain tube is not easily accessible. If you suspect a frozen drain tube a professional service must assess the problem.

Ice Maker Not Filling Properly

An ice maker that doesn’t fill properly can leak water that ultimately builds up and forms frost. You may find that if you clean Sub-Zero ice maker this will eliminate leaks and frost. If a cleaning doesn’t restore proper ice maker function, professional service is required.

Defrost Element Failure

If your refrigerator freezer won’t defrost after these interventions, an element in the defrost system may have failed. 

These defrost element malfunctions can be responsible for a Sub-Zero refrigerator freezer not defrosting and require professional replacement:

  • Faulty defrost timer: Defrost system won’t start or stop as needed.
  • Broken defrost heater: Won’t melt the frost on evaporator coils, causing buildup in the freezer.
  • Failed defrost thermostat: Can’t monitor freezer temperature accurately or signal defrost heater properly, allowing frost to accumulate.

How to Manually Defrost a Sub-Zero Freezer

If you need to remove an excess of frost buildup, you can manually defrost your Sub-Zero refrigerator freezer. While some models allow you to defrost specific compartments, consult your user manual to determine if this is possible for your model freezer. Otherwise, the entire freezer must be defrosted as a whole.

Follow these steps to manually defrost a Sub-Zero freezer:

  1. Empty the freezer. 
  2. Place towels in and around the freezer on the floor to absorb any water.
  3. Leave the freezer door open. It may take several hours to defrost completely.
  4. Once defrosted, close the freezer door and allow 24 hours for it to reach its normal temperature before replacing frozen items. 

The team at DeserTech can resolve most Sub-Zero issues, from defrosting problems to part malfunctions. Schedule your expert service call today.

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