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Error code reference

Samsung Air Conditioner Error Code E403

Prohibit starting by low pressure

Samsung codesSamsung air conditioner codes

Prohibit starting by low pressure - low pressure sensor value below 3.1 kg/cm2G during cooling or below 2.6 kg/cm2G during heating for 3 consecutive seconds before pump down start.

First step from the service manual

Measure pressure using manifold gauge when system is stopped.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What E403 means on a Samsung air conditioner

Error code E403 on a Samsung air conditioner is a low pressure lockout fault. The system monitors suction-side refrigerant pressure through a low pressure sensor, and E403 triggers when that sensor reads below 3.1 kg/cm2G during a cooling operation or below 2.6 kg/cm2G during a heating operation for 3 consecutive seconds before pump down begins. The control board interprets these readings as an unsafe operating condition and prohibits the compressor from starting to prevent damage from running on insufficient refrigerant charge or a restricted system.

The most frequent root cause of E403 is low refrigerant charge, typically the result of a leak in the refrigerant circuit at service valves, flare connections, or coil joints. A refrigerant shortage drops suction pressure below the threshold values the system requires before allowing startup. Other causes include a blocked or restricted filter drier or expansion valve that reduces pressure on the low side, or a faulty low pressure sensor that is sending an inaccurate signal to the control board even when actual system pressure is adequate. A malfunctioning sensor can produce false E403 faults without any actual refrigerant loss.

The correct first diagnostic step is to connect a manifold gauge set to the system service ports while the unit is stopped and measure static pressure. If static pressure is normal for the refrigerant type and ambient temperature, the sensor or its wiring circuit should be suspected. If pressure is genuinely low, the system should be leak-checked before any refrigerant is added, as topping off a leaking system is only a temporary measure and refrigerant handling requires proper certification.

Source: manufacturer service documentation.

Common causes of E403

  1. 01

    Low refrigerant charge due to a leak

    Wiring / connection

    A leak at flare connections, service valves, or coil joints allows refrigerant to escape, dropping suction pressure below the 3.1 kg/cm2G (cooling) or 2.6 kg/cm2G (heating) threshold. Connect a manifold gauge to confirm low static pressure, then perform a leak search before recharging.

  2. 02

    Faulty low pressure sensor

    Part replacement

    A defective low pressure sensor can report falsely low pressure values to the control board even when actual system pressure is within normal range. If manifold gauge readings are normal but E403 persists, the sensor and its wiring should be tested and replaced if defective.

  3. 03

    Restricted or blocked expansion valve

    Part replacement

    A clogged or stuck-closed expansion valve reduces refrigerant flow and can cause suction pressure to drop sharply on the low side. This restriction will produce abnormally low suction pressure readings on the manifold gauge despite adequate refrigerant charge.

  4. 04

    Blocked or saturated filter drier

    Part replacement

    A restricted filter drier creates a pressure drop in the liquid line that can propagate to the low side of the system, reducing suction pressure below the sensor threshold. A significant temperature differential across the drier is a common indicator of this condition.

  5. 05

    Wiring fault in the sensor circuit

    Wiring / connection

    Damaged, corroded, or loose wiring between the low pressure sensor and the control board can cause erroneous low-pressure signals. Inspect the sensor connector and wiring harness for corrosion, breaks, or loose terminals before condemning the sensor or refrigerant circuit.

See the test procedure for each cause

Frequently asked questions about E403

What does E403 mean on a Samsung air conditioner?
E403 indicates the system has detected suction-side refrigerant pressure below the minimum required threshold before pump down start. Specifically, the low pressure sensor read below 3.1 kg/cm2G during cooling or below 2.6 kg/cm2G during heating for 3 consecutive seconds. The control board blocks the compressor from starting to prevent mechanical damage. The fault points to either a low refrigerant charge or a problem with the pressure sensor itself.
Can I fix E403 on my Samsung air conditioner myself?
Some basic checks, such as inspecting wiring to the low pressure sensor and verifying the sensor connector is secure, can be done without special tools. However, diagnosing and correcting low refrigerant pressure requires a manifold gauge set and EPA certification to handle refrigerants legally. If the system has lost refrigerant due to a leak, a certified HVAC technician must locate the leak, repair it, and recharge the system.
Is it safe to keep running my air conditioner with an E403 error?
No. The E403 fault is a protective lockout that prevents the compressor from starting specifically because running on low refrigerant pressure can cause severe compressor damage. The unit will refuse to operate normally until the fault condition is resolved. Attempting to override the lockout or repeatedly resetting the unit without addressing the root cause risks costly compressor failure.
How much does it cost to repair an E403 error on a Samsung air conditioner?
Repair costs vary widely depending on the root cause. A sensor replacement typically runs in the range of $100 to $250 including labor. If the system needs a leak repair and refrigerant recharge, costs commonly range from $200 to $600 or more depending on the leak location, refrigerant type, and quantity required. A blocked expansion valve or filter drier replacement will generally fall in the $150 to $400 range for parts and labor.
Will resetting my Samsung air conditioner clear the E403 error?
A power reset may temporarily clear the fault display, but E403 will return immediately if the underlying pressure condition still exists. Because the sensor continuously monitors suction pressure and the fault triggers within 3 seconds of the threshold being breached, the lockout will reactivate as soon as the system attempts to start. A reset is only a valid resolution after the actual cause, whether a refrigerant leak, faulty sensor, or restriction, has been diagnosed and corrected.

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