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Error code reference

Samsung Air Conditioner Error Code 477

Liquid compressor protection control

Samsung codesSamsung air conditioner codes

Liquid compressor protection control - protective control operation if refrigerants inflow by digital compressor.

First step from the service manual

Check Sump sensor/Discharge sensor connection; check sensor position on compressor; check Main EEV and EVI EEV normal operation; check Discharge Check Valve leakage.

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

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What 477 means on a Samsung air conditioner

Samsung error code 477 indicates a liquid compressor protection event triggered by refrigerant liquid inflow into a digital compressor. Under normal operation, only refrigerant vapor should enter the compressor. When liquid refrigerant enters the compression chamber, it cannot be compressed like gas and creates a hydraulic hammering effect known as liquid slugging. This condition places severe mechanical stress on internal compressor components, including pistons, valves, and connecting rods, and can result in catastrophic compressor failure if the protective control does not intervene in time. The system activates this protective control to shut down or limit compressor operation before damage occurs.

The primary causes of liquid refrigerant inflow involve failures in the expansion valve system or sensor feedback errors that cause incorrect refrigerant metering. The Main EEV (electronic expansion valve) and the EVI EEV (economizer vapor injection expansion valve) both regulate refrigerant flow into the circuit. If either valve fails to close properly or is sending incorrect flow rates, excess liquid refrigerant can reach the compressor. A leaking discharge check valve can also allow high-pressure refrigerant to migrate backward through the system, contributing to liquid accumulation at the compressor inlet.

Sensor-related faults are another significant factor. The sump sensor monitors the temperature at the bottom of the compressor, where liquid refrigerant tends to pool, while the discharge sensor monitors outlet temperature. If either sensor has a poor connection, is incorrectly positioned on the compressor body, or is providing inaccurate readings, the system may misread refrigerant state and allow liquid slugging to occur undetected until protection triggers. Diagnosing code 477 requires verifying sensor connections and placement, testing EEV operation, and inspecting the discharge check valve for leakage.

Source: manufacturer service documentation.

Common causes of 477

  1. 01

    Main EEV malfunction or improper flow control

    Part replacement

    If the main electronic expansion valve fails to regulate refrigerant flow correctly, excess liquid refrigerant can reach the compressor. Check for valve coil resistance, proper electrical connection, and mechanical response during operation.

  2. 02

    Sump or discharge sensor connection fault

    Wiring / connection

    Loose, corroded, or incorrectly positioned sensors can provide false temperature readings to the control board, preventing the system from detecting liquid accumulation at the compressor in time. Inspect connectors and verify sensor placement on the compressor body.

  3. 03

    EVI EEV malfunction

    Part replacement

    The economizer vapor injection expansion valve controls refrigerant entering the intermediate injection port. A stuck-open or improperly calibrated EVI EEV can flood the compressor with liquid refrigerant. Verify normal operation and valve response.

  4. 04

    Discharge check valve leakage

    Part replacement

    A leaking discharge check valve allows high-pressure refrigerant to back-flow through the system during off cycles, increasing liquid refrigerant presence near the compressor inlet at startup. Inspect the valve for proper seating and signs of refrigerant migration.

  5. 05

    Incorrect refrigerant charge

    Wiring / connection

    An overcharged refrigerant circuit increases the likelihood of liquid carryover to the compressor, especially at low load conditions. Verify system refrigerant charge against rated specifications using manifold gauges.

See the test procedure for each cause

Frequently asked questions about 477

What does 477 mean on a Samsung air_conditioner?
Error code 477 on a Samsung air conditioner indicates that the liquid compressor protection control has activated due to refrigerant liquid entering the digital compressor. Compressors are designed to compress only refrigerant vapor, and liquid inflow can cause severe internal damage through a condition called liquid slugging. The system intervenes automatically to protect the compressor from mechanical failure.
Can I fix Samsung error code 477 myself?
Some portions of the diagnosis, such as checking sensor connections and verifying sensor positioning on the compressor body, can be performed by a knowledgeable DIYer. However, inspecting and testing the EEV valves, checking the discharge check valve for leakage, and verifying refrigerant charge require specialized tools and refrigerant handling certification. It is strongly recommended to have a certified HVAC technician handle the full repair.
Is it safe to run the air conditioner with error code 477 active?
No, you should not continue operating the unit while error code 477 is active. The protective control is designed to prevent compressor damage from liquid slugging, and bypassing or ignoring it risks destroying the compressor entirely. Continued operation could also create unsafe refrigerant pressure conditions within the system.
Will resetting the unit clear Samsung error code 477?
A simple power reset may temporarily clear the fault and allow the unit to restart, but if the underlying cause such as a faulty EEV, sensor issue, or leaking check valve is not corrected, the error will return. In many cases, liquid slugging damage accumulates over multiple events, so resolving the root cause before restarting is critical to protecting the compressor long-term.
How much does it cost to repair Samsung error code 477?
Repair costs vary widely depending on the root cause identified during diagnosis. Sensor replacements or connection repairs are typically the least expensive, often in the range of $100 to $300 including labor. EEV replacements or discharge check valve repairs can range from $200 to $600 or more. If the compressor has already sustained liquid slugging damage and requires replacement, costs can reach $800 to $2,000 or higher depending on the unit.

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