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What do Sub-Zero 600 series error codes 20 to 24 mean?
On Sub-Zero 600-3 series built-in refrigerators such as the 650, error codes 20 to 24 are defrost system faults. 21 means defrost overheat and 24 means defrost under-heat. Codes 20, 22 and 23 also involve missing voltage feedback at defrost start. Defrost heater and wiring repairs need a technician.
What the code means
Sub-Zero's 600-3 Series service manual (serials after M2603255) lists: 20, defrost under-heat with no voltage feedback through the gray/white wire at defrost start; 21, defrost overheat; 22, no voltage feedback through the gray/white wire at defrost start; 23, defrost overheat with no voltage feedback at defrost start; 24, defrost under-heat. The manual's tests cover the defrost heater, defrost terminator, thermistor mounting and control-board wiring.
Safe homeowner checks
- Write down the code and the model and serial numbers.
- Keep the freezer closed and watch for frost buildup or rising temperatures.
- Don't chip ice or try to force a defrost.
- Do not open panels, test wiring, or replace parts yourself.
When to call a technician
Call a technician for any 20–24 code. Defrost heater, terminator and line-voltage wiring tests are technician-only work.
OEM source
Sub-Zero 600-3 Series Service Manual (after serial M2603255), Error Code Table and Error Code Troubleshooting Guide (Sub-Zero Service Central, model 650), PDF p.113-114: https://service.subzero.com/KnowledgeBase/External?i=d&t=GROUP&v=650
Is your Sub-Zero 600 series showing a defrost code? Call Home Alliance at (877) 777-0796 to book a Sub-Zero refrigerator technician. Customers rate us 4.91/5 from 12,574 reviews.
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Trademark disclaimer: Sub-Zero and Wolf are registered trademarks of Sub-Zero Group, Inc. Home Alliance is an independent service provider and is not affiliated with, endorsed by, or an authorized agent of Sub-Zero Group, Inc.. Brand names are used only to identify the appliances we service.
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