Error code reference

Sub-Zero Refrigerator Error Code 21

Check Zone X Defrost Bi-metal for Proper Operation.

SourceSub-Zero Pro-Series Refrigerator - Service Manual (Model 648PRO)p. 3-30, 8-5

Sub-Zero codes Sub-Zero refrigerator codes

Diagnostic procedure

The full 21 procedure

Step 1 is visible so you can confirm you are on the right page. The remaining steps, the ones that tell you whether to actually replace a part, unlock with any pass.

MyPros+ · DiagnosticsStep 1 preview

First diagnostic step

Inspect defrost bi-metal for proper operation in the indicated zone.

SourceSub-Zero Pro-Series Refrigerator - Service Manual (Model 648PRO)p. 3-30, 8-5

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More steps, wiring diagram references, and verified part numbers

Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.

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Where this code is documented

25 manuals in the MyPros+ library document this code for Sub-Zero refrigerator.

Models covered by the manuals that document this code

More models are covered than are listed here.

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The full 21 procedure

Where this code is documented

Models covered by the manuals that document this code

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