Error code reference

Samsung Heat Pump Error Code E121

Detection of reverse phase or missing phase of 3-phase power

Detection of reverse phase or missing phase of 3-phase power - phase order reversed or one/all phase voltages not present.

First step from the service manual

Check power of 3-phase detection part on outdoor unit PCB; verify voltage between CN82 power cable terminals (red-white/white-black/red-black) is approximately 380V.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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Step-by-step tests with expected resistance, voltage, and continuity values
Wiring diagram references and connector pinouts from the OEM service manual
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E121 on my Samsung Heat Pump

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Detection of reverse phase or missing phase of

From Service Manual 326063, p.35:

1.Check power of 3-phase detection part on outdoor unit PCB; verify voltage between CN82 power cable terminals (red-white/white-black/red-black) is approximately 380V.

2.Measure door lock assembly resistance across the PTC terminals. Expected: ~200 ohms cold, rising sharply once energized.

3.Inspect strike and latch alignment. A warped door or misaligned strike prevents the switch stack from closing in the correct sequence.

Part DC34-00024B

Door lock assembly

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First step from the service manual

Get the full diagnostic procedure for E121.

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