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Error code reference

Samsung Air Conditioner Error Code E425

Reverse phase of 3-phase power

Samsung codesSamsung air conditioner codes

Reverse phase of 3-phase power - phase order reversed or one or more phase voltages not present at 3-phase detection circuit.

First step from the service manual

Check main voltage at CN82 power cable (red-white, white-black, red-black) for approximately AC 380V.

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

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What E425 means on a Samsung air conditioner

Error code E425 on Samsung commercial air conditioning systems indicates a reverse phase condition on the 3-phase power supply. The unit's internal phase detection circuit, connected at connector CN82, continuously monitors the three legs of the incoming AC power. When the phase sequence is reversed (meaning the rotational order of the three phases is incorrect) or when one or more phase voltages are absent or significantly reduced, the system triggers E425 and shuts down to prevent compressor and motor damage. Three-phase motors and compressors are designed to operate in a specific phase rotation order, and running them in reverse rotation can cause immediate mechanical damage.

The first diagnostic step is to check the main voltage at the CN82 power cable, measuring across all three conductor pairs: red-white, white-black, and red-black. Each pair should read approximately AC 380V. If all three readings are present and correct but the error persists, the phase sequence itself may be reversed, which requires swapping two of the three incoming supply lines at the disconnect or breaker. If any reading is absent or significantly low, there is an open phase condition caused by a blown fuse, tripped breaker, failed contactor, or a wiring fault upstream of the unit. The phase detection circuit will also trigger this code if supply voltage is unstable or drops below acceptable thresholds on any leg.

Source: manufacturer service documentation.

Common causes of E425

  1. 01

    Incorrect phase sequence at the disconnect or breaker

    Wiring / connection

    If two of the three supply lines were swapped during installation or after electrical work, the phase rotation will be reversed. This is confirmed when all three voltages at CN82 measure approximately 380V but the error remains, and is corrected by swapping any two of the three incoming supply conductors.

  2. 02

    Open phase due to blown fuse or tripped breaker

    Wiring / connection

    A blown fuse or tripped single-pole breaker on one leg of the 3-phase supply will cause one conductor to read near 0V at CN82, triggering this code. Check the voltage across all three conductor pairs (red-white, white-black, red-black) at CN82 and inspect upstream overcurrent protection.

  3. 03

    Failed or damaged wiring between disconnect and CN82

    Part replacement

    A broken wire, loose terminal, or corroded connector in the supply cable can interrupt one phase before it reaches the CN82 detection circuit. Inspect the power cable and connections for visible damage, corrosion, or loose terminals.

  4. 04

    Faulty contactor or relay dropping one phase

    Part replacement

    A contactor with a burned or welded contact can fail to pass one leg of the 3-phase supply through to the unit. Check contactor operation and measure voltage on both the line and load sides of any contactors in the power path.

  5. 05

    Defective CN82 phase detection circuit on the control board

    Part replacement

    If all three voltages at CN82 measure approximately 380V and the phase sequence has been confirmed correct, the phase detection circuit on the main control board may be faulty. This is a less common cause and should be considered only after all wiring and supply conditions have been ruled out.

See the test procedure for each cause

Frequently asked questions about E425

What does E425 mean on a Samsung air_conditioner?
E425 indicates a reverse phase or missing phase condition on the 3-phase power supply. The unit's phase detection circuit at connector CN82 has detected that the phase sequence is incorrect or that one or more of the three AC supply voltages (nominally 380V each) is absent. The system shuts down automatically to prevent damage to the compressor and motors.
Can I fix the E425 error myself, or do I need a professional?
Diagnosing E425 involves working directly with 380V 3-phase power, which is dangerous and should only be handled by a qualified electrician or licensed HVAC technician. A technician will measure voltages at the CN82 connector across all three conductor pairs and check phase rotation. If the fix is simply swapping two supply conductors to correct phase sequence, a qualified professional can do this quickly, but it must not be attempted by an untrained person.
Will resetting the unit clear the E425 error?
A simple reset will not clear E425 if the underlying power supply problem still exists. The phase detection circuit monitors incoming power continuously, so the error will return immediately after restart if the phase sequence is still reversed or a phase is still missing. The root cause in the electrical supply must be corrected first before the unit will operate normally.
Is it safe to keep running the air conditioner with an E425 error?
No. The unit will not run while displaying E425 because the shutdown is a protective measure. Attempting to force the unit to operate with reversed phase rotation would cause the compressor and fan motors to run in the wrong direction, leading to rapid mechanical failure. An open phase condition can also cause single-phasing, which overheats and destroys motor windings. The shutdown should be respected until the power supply issue is resolved.
How much does it cost to repair an E425 error on a Samsung commercial air conditioner?
Repair costs vary depending on the root cause. If the issue is simply swapping two supply conductors for incorrect phase sequence, labor costs for a technician visit may range from $100 to $300. If a fuse, breaker, or contactor needs replacement, parts and labor could range from $150 to $600 or more. A main control board replacement, needed only if the phase detection circuit itself is faulty, is typically the most expensive repair and can range from $400 to over $1,000 including labor.

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