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Error code reference

Samsung Air Conditioner Error Code E303

Communication error between indoor unit and outdoor unit after completion of tracking

Samsung codesSamsung air conditioner codes

Communication error between indoor unit and outdoor unit after completion of tracking - no communication for 2 minutes during operation.

First step from the service manual

Press reset key (K3) on outdoor unit PCB and check for indoor unit response during tracking.

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

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What E303 means on a Samsung air conditioner

Samsung E303 is a communication fault that triggers when the indoor unit and outdoor unit lose contact for a continuous period of 2 minutes during active operation. This is distinct from a startup communication failure: the tracking sequence (the initial handshake between units when the system powers on) has already completed successfully, meaning the two units were communicating at some point. The fault develops mid-operation, indicating an intermittent or newly introduced disruption in the communication pathway rather than a wiring problem that was present from the beginning.

The communication signal between indoor and outdoor units travels over a dedicated signal wire within the interconnecting cable, often referred to as the serial communication line. If this line experiences an open circuit, a short to ground, excessive resistance, or electromagnetic interference, the signal can drop out long enough to trigger the 2-minute timeout threshold. Faulty PCBs on either the indoor or outdoor unit can also generate this fault if a communication IC or its associated circuitry degrades during operation, particularly under thermal stress after the system has been running for some time.

The first diagnostic step involves pressing the reset key (K3) on the outdoor unit PCB and observing whether the indoor unit responds during the tracking sequence. A successful re-tracking response points toward a recoverable communication glitch, a marginal signal line connection, or intermittent PCB behavior. A failure to re-establish tracking after the reset points more directly toward a damaged signal wire, a failed PCB component, or a severe voltage irregularity on the communication line that is preventing signal transmission entirely.

Source: manufacturer service documentation.

Common causes of E303

  1. 01

    Damaged or loose communication wiring

    Wiring / connection

    The signal wire in the interconnecting cable between indoor and outdoor units may have a loose terminal, a pinched section, or a break in the conductor. Inspect the full length of the cable and check all terminal connections at both units for corrosion, looseness, or visible damage.

  2. 02

    Faulty outdoor unit PCB

    Part replacement

    The outdoor unit control board contains the communication circuitry that transmits and receives signals. If this board has a failed communication IC or heat-damaged components, it may lose the ability to maintain the signal after the system has been running for a while.

  3. 03

    Faulty indoor unit PCB

    Part replacement

    The indoor unit PCB is equally responsible for maintaining communication. A degraded communication component on the indoor board can cause the signal to drop mid-operation even if the outdoor unit hardware is functioning correctly.

  4. 04

    Electromagnetic interference on the signal line

    Wiring / connection

    If the communication wire runs in close proximity to high-voltage power cables or other interference sources, induced noise can corrupt the signal enough to break communication. Check the routing of the interconnecting cable and ensure it is separated from power conductors.

  5. 05

    Power supply irregularity affecting communication voltage

    Wiring / connection

    Unstable or insufficient supply voltage to either unit can disrupt the communication circuitry during operation. Measure the supply voltage at both the indoor and outdoor units under load to confirm it is within the specified operating range.

See the test procedure for each cause

Frequently asked questions about E303

What does E303 mean on a Samsung air conditioner?
E303 indicates a communication failure between the indoor and outdoor units that occurred during operation, after the initial startup tracking sequence had already completed successfully. The system detected no communication signal for 2 continuous minutes and shut down as a protective measure. The fault points to the signal wiring, one of the two control boards, or an external interference source disrupting the communication line.
Will pressing the reset key (K3) clear the E303 error?
Pressing the reset key K3 on the outdoor unit PCB is the correct first step and may clear the fault if the communication dropout was caused by a temporary glitch or a marginal connection that re-seats itself. If the indoor unit responds correctly during the tracking sequence after the reset, the system may resume normal operation. However, if the underlying cause is a damaged wire or a failing PCB, the error will return during operation once the fault condition develops again.
Is it safe to keep using the air conditioner when E303 appears?
No. When E303 is active, the system has already shut down or is operating in a degraded state because the indoor and outdoor units cannot coordinate safely. Attempting to force operation without resolving the communication fault can cause the system to behave unpredictably, potentially leading to compressor damage or other component failures. The fault should be diagnosed and resolved before returning the unit to normal use.
How much does it cost to fix a Samsung air conditioner E303 error?
Repair costs depend on the root cause. If the issue is a loose terminal or damaged communication wire, the cost is typically limited to a service call fee in the range of $75 to $150. If a control board needs replacement, parts and labor combined can range from $200 to $600 or more depending on the specific unit model and local labor rates. Getting a diagnostic assessment before authorizing parts replacement is strongly recommended.
What is the difference between E303 and other Samsung communication error codes?
E303 specifically indicates that communication failed after the initial tracking sequence between indoor and outdoor units was already completed. This separates it from communication faults that occur at startup before tracking finishes, which point more directly to a wiring or connection problem that was present before the system powered on. The mid-operation nature of E303 suggests intermittent causes such as thermal stress on a PCB, a marginal wire connection that vibrates loose, or interference that develops under certain operating conditions.

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