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It means an error with the gas/easy/PH sensor. Samsung lists the description once for C-10, C-11 and C-12 together, and the entry is for current-generation microwaves.
Begin by disconnecting the microwave, either at the plug or at the breaker. Then work out whether anything wet got into it. If a spill or steam from a cooktop reached the unit, it needs to dry before power returns. If not, waiting 60 seconds is enough before you reconnect it.
Request service.
C-10 and C-11 are the other two gas/easy/PH entries. C-22 is a temperature sensor error. C-71 is a steam sensor error.
Microwave repair for San Francisco and the Bay Area
For a Samsung unit that keeps showing C-12, the number is (415) 969-6153, and the page for Samsung microwave repair explains the service. Give the code, your model number and the reset you carried out.
Model compatibility: Samsung reuses codes across series and model years, so C-12 / C12 may mean something different on another appliance or generation. Confirm this against your model’s documentation and record your full model number before acting.
