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HomeRepair HelpSub Zero Refrigerator RepairSub Zero Refrigerator has frost or moisture buildup around the door Repair
Sub Zero Refrigerator has frost or moisture buildup around the door
Frost and moisture around the Sub Zero refrigerator door means warm, humid air is getting past the mullion flap and freezing where it meets the cabinet. The most likely cause is a failed mullion heater flap that no longer heats to melt condensation—test it for electrical continuity with a multimeter and replace it if it’s open. Next check the door support and door guide for wear or misalignment, since damaged parts can prevent the flap from seating. A twisted or torn door gasket will also let warm air in and is a common cause of frost buildup. Less often, frost follows leaving a door open for several hours and should clear after a defrost cycle. If you notice poor sealing, a fridge door not sealing, or a refrigerator door not closing properly, replace the faulty support, guide, or gasket to restore the seal. Enter your model number on RepairClinic.com to find the exact replacement mullion heater, support, guide, or gasket for your unit.
01 - Sub Zero Refrigerator Mullion Heater
A defective mullion heater flap may not be able to heat up periodically to melt any frost or moisture that forms on the flap due to increases in room humidity. You can use a multimeter to test the mullion heater for electrical continuity to determine if the component is working. If the mullion heater has no electrical continuity you should replace it with a new one.
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Common
02 - Sub Zero Refrigerator Door Support
If the mullion heater flap has frost or moisture buildup, it's possible the door suport is damaged or misaligned and not allowing the flap to form a tight seal between the refrigerator doors. Inspect the door support for wear or damage and replace if necessary.
Common
03 - Sub Zero Refrigerator Door Guide
If the mullion heater flap has frost or moisture buildup, it's possible the door guide is damaged or misaligned and not allowing the flap to form a tight seal between the refrigerator doors. Inspect the door guide for wear or damage and replace if necessary.
Common
04 - Sub Zero Refrigerator Door Gasket
A door gasket should form an airtight seal around the appliance's frame to keep the cold air in and the warm air out. If the door gasket is twisted or torn, gaps can form that will allow warm air in, resulting in the freezer not freezing properly. Inspect the door gasket for any damage and replace with a new one if necessary.
Common
05 - Refrigerator or freezer door left open
If the freezer or refrigerator door was left open for an extended period of time (more than 4 hours), frost may have accumulated on the food and around the door opening. The frost should go away after the door is closed and the refrigerator goes through a defrost cycle.
Common
Frequently Asked Questions
Why is my refrigerator getting frost or moisture around the door?
How do I test the mullion heater on my Sub Zero refrigerator?
Will replacing the door gasket stop the frost and moisture?
My refrigerator door is not closing properly. How do I fix a misaligned door?
How do I find the correct replacement part on RepairClinic.com using my model or part number?
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