Error code reference

Samsung Air Conditioner Error Code P421

Low pressure protection control-low pressure sensor below 0.7 kg/cm²G (cooling) or 0.2 kg/cm²G (heating).

SourceSamsung Air Conditioner - Service Manual: Troubleshooting (AVMC4H071EA)p. 12-73

Samsung codes Samsung air conditioner codes

Diagnostic procedure

The full P421 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

Check if all service valves are open; check PWM valve coil and connector.

SourceSamsung Air Conditioner - Service Manual: Troubleshooting (AVMC4H071EA)p. 12-73

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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

2 manuals in the MyPros+ library document this code for Samsung air conditioner.

Models covered by the manuals that document this code

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The full P421 procedure

Where this code is documented

Models covered by the manuals that document this code

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