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Error code reference

Samsung Air Conditioner Error Code P426

Outdoor unit reverse phase detection 2 error.

Samsung codesSamsung air conditioner codes

Outdoor unit reverse phase detection 2 error.

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What P426 means on a Samsung air conditioner

The P426 error code on a Samsung air conditioner indicates an outdoor unit reverse phase detection error, specifically classified as a second reverse phase fault. This code is generated by the outdoor unit's control board when it detects that the three-phase power supply is connected in an incorrect phase sequence. Three-phase systems require power to arrive in a specific rotational order (typically L1, L2, L3) to ensure that compressors and fan motors spin in the correct direction. When the phase sequence is reversed or a phase is out of order, the control board triggers this protection fault to prevent mechanical damage.

The outdoor unit's main PCB continuously monitors incoming three-phase voltage to verify proper phase rotation. If the phase sequence is detected as incorrect, the board will shut down the unit and display P426 rather than allow components like the scroll compressor to operate in reverse rotation, which can cause rapid and severe mechanical damage. This is a protective shutdown, not a component failure in itself, though repeated occurrences or ignored faults can lead to compressor damage over time.

Common triggers include incorrect wiring at installation, a recent change or repair to the electrical supply, a tripped or replaced breaker that was reconnected with phases in the wrong order, or a utility-side phase issue. Loose or corroded terminal connections at the outdoor unit's power input can also cause intermittent phase detection errors by introducing voltage imbalance or momentary phase loss.

Source: manufacturer service documentation.

Common causes of P426

  1. 01

    Incorrect phase wiring at installation or service

    Wiring / connection

    The three-phase power leads (L1, L2, L3) may have been connected to the outdoor unit terminals in the wrong sequence. This is the most common cause and is confirmed by checking the phase rotation with a phase sequence tester at the unit's terminal block.

  2. 02

    Breaker or disconnect reconnected in wrong phase order

    Wiring / connection

    If the outdoor unit's circuit breaker or disconnect switch was recently replaced or reset, the incoming phases may have been reconnected in an incorrect order. Inspecting the wiring at the breaker panel and disconnect box can identify this issue.

  3. 03

    Loose or corroded power terminal connections

    Wiring / connection

    Loose terminals at the outdoor unit's power input block can cause voltage irregularities that the phase detection circuit interprets as a phase reversal. Visually inspect and torque all incoming power terminals to specification.

  4. 04

    Utility supply phase issue

    Wiring / connection

    In some cases the power company's supply may have a phase irregularity or a temporary phase reversal following utility maintenance or an outage. Contact the utility provider to verify proper phase sequence at the meter if wiring checks out correctly.

  5. 05

    Faulty outdoor unit main PCB

    Part replacement

    If the phase sequence has been confirmed correct by a phase rotation meter and all wiring checks out, the phase detection circuit on the outdoor unit's control board may itself be defective. Board replacement would be required in this scenario.

See the test procedure for each cause

Frequently asked questions about P426

What does P426 mean on a Samsung air conditioner?
P426 indicates an outdoor unit reverse phase detection error, specifically a second reverse phase fault. The outdoor unit's control board has detected that the incoming three-phase power supply is connected in an incorrect phase sequence. This is a protective shutdown designed to prevent the compressor and fan motors from running in reverse rotation, which would cause serious mechanical damage.
Can I fix the P426 error myself?
Diagnosing and correcting a phase sequence issue requires working directly with three-phase high-voltage electrical wiring, which is dangerous without proper training and equipment. A licensed electrician or certified HVAC technician should inspect the power wiring at the outdoor unit's terminal block and upstream connections. If the issue is simply swapped wires at a terminal, the fix itself is straightforward for a professional.
Is it safe to keep running my AC with a P426 error?
No. The unit will not operate while P426 is active because the control board has shut it down as a protective measure. Attempting to bypass or ignore this fault and force the system to run could result in the compressor operating in reverse, which causes rapid and potentially irreversible internal damage. The fault should be resolved before restarting the system.
Will resetting the unit clear the P426 error?
A power reset may temporarily clear the fault code, but if the underlying phase sequence issue has not been corrected, the error will return as soon as the unit attempts to operate and the control board re-checks the incoming phase rotation. The root cause must be identified and corrected for the unit to run normally.
How much does it cost to repair a P426 error on a Samsung air conditioner?
If the fix is simply correcting swapped wiring at the terminal block or disconnect, costs are primarily for a service call and labor, typically ranging from $75 to $200 depending on the technician and region. If the outdoor unit's main control board has failed and requires replacement, parts and labor combined can range from $300 to $700 or more depending on the specific unit model. An electrician's fee may apply separately if utility or panel wiring is involved.

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