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Error code reference

Samsung Air Conditioner Error Code RED_ON_GRN_FLICKER

Communication error (indoor-outdoor)

Samsung codesSamsung air conditioner codes

Communication error (indoor-outdoor)

First step from the service manual

Check communication cable connections between indoor and outdoor units

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

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What RED_ON_GRN_FLICKER means on a Samsung air conditioner

The RED_ON_GRN_FLICKER error code on a Samsung air conditioner indicates a communication fault between the indoor and outdoor units. This is signaled by the red LED remaining on while the green LED flickers, which is the system's way of flagging a breakdown in the serial communication link that allows the two units to exchange operational data. This data link carries signals for compressor status, sensor readings, control commands, and system feedback, so when communication fails, the unit cannot operate safely or efficiently and will shut down.

The communication between indoor and outdoor units typically runs over a dedicated two-wire or three-wire cable connecting the control boards of both units. If this cable is damaged, loose, corroded, or incorrectly wired, the signal cannot pass reliably. Electrical interference from nearby wiring, poor ground connections, or a voltage drop along the cable can also disrupt the communication signal. In some cases, the fault lies not in the wiring itself but in the control board of either the indoor or outdoor unit, where a failed communication circuit prevents proper data exchange.

Diagnosing this error starts at the communication cable connections on both the indoor and outdoor unit terminals. Technicians should inspect for loose terminal screws, corrosion, pinched or nicked insulation, and confirm that the wiring matches the correct terminal assignments for the installation. If wiring checks out, the next step is to evaluate the control boards for damage or failure.

Source: manufacturer service documentation.

Common causes of RED_ON_GRN_FLICKER

  1. 01

    Loose or disconnected communication cable

    Wiring / connection

    The communication wire terminals on either the indoor or outdoor unit control board may have come loose or been pulled free. Check that all terminal screws are tight and that wires are fully seated at both ends.

  2. 02

    Damaged communication cable

    Part replacement

    Physical damage to the cable running between units, such as pinching, cuts, or rodent damage, can break or short the communication signal. Inspect the full cable run for any visible damage or exposed conductors.

  3. 03

    Corroded or oxidized terminal connections

    Wiring / connection

    Moisture exposure at outdoor unit terminals can cause corrosion that increases resistance on the communication line and disrupts signal integrity. Look for green or white oxidation on terminal screws and wire ends.

  4. 04

    Incorrect wiring or terminal assignment

    Wiring / connection

    If the communication cable was recently serviced or installed incorrectly, wires may be on the wrong terminals. Verify that the wiring matches the terminal labeling on both the indoor and outdoor control boards.

  5. 05

    Failed indoor or outdoor control board

    Part replacement

    If wiring checks out completely, the communication circuit on one of the control boards may have failed. A burned component or failed IC on the board will prevent proper signal transmission and requires board replacement.

See the test procedure for each cause

Frequently asked questions about RED_ON_GRN_FLICKER

What does RED_ON_GRN_FLICKER mean on a Samsung air conditioner?
The RED_ON_GRN_FLICKER code signals a communication error between the indoor and outdoor units of your Samsung air conditioner. It is indicated by the red LED staying on while the green LED flickers. The system shuts down because the two units can no longer exchange the control signals needed to operate safely. The fault is typically in the communication cable or the control boards of one or both units.
How do I fix the RED_ON_GRN_FLICKER communication error on my Samsung AC?
Start by powering off the system and inspecting the communication cable connections at both the indoor and outdoor units, tightening any loose terminal screws and looking for corrosion or damaged wiring. If the connections appear clean and secure, inspect the cable run between units for physical damage. If wiring is intact and correctly terminated, the fault may be in a control board, which will require board-level diagnosis or replacement by a qualified technician.
Is it safe to keep running my Samsung air conditioner with the RED_ON_GRN_FLICKER error showing?
No, the system will generally not continue running when this error is active, as it requires communication between units to operate safely. Attempting to force operation without resolving the fault could cause further damage to the control boards or other components. You should address the communication fault before returning the unit to service.
Will resetting my Samsung air conditioner clear the RED_ON_GRN_FLICKER error?
A power reset may temporarily clear the error display, but the code will return if the underlying communication fault is not resolved. Resetting without fixing the wiring or board issue is not a reliable solution. The root cause, whether a loose connection, damaged cable, or failed control board, must be corrected for the system to operate without returning the error.
How much does it cost to repair a Samsung air conditioner with a communication error?
Repair costs vary depending on the cause. If the issue is simply a loose or corroded connection, a service call to inspect and reseat the wiring may cost in the range of $75 to $150. If the communication cable needs replacement, expect $100 to $250 depending on cable length and labor. A failed control board is the most expensive repair, typically ranging from $200 to $600 or more depending on the board and labor involved.

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