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Error code reference

Samsung Air Conditioner Error Code E407

PWM discharge temperature sensor OPEN/SHORT error. Detected when outdoor temp over -10°C. Error level

Samsung codesSamsung air conditioner codes

PWM discharge temperature sensor OPEN/SHORT error. Detected when outdoor temp over -10°C. Error level: Over 4.95V (-30°C), below 0.5V (151°C).

First step from the service manual

Check sensor connector; measure resistance across both terminals.

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

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What E407 means on a Samsung air conditioner

The E407 error code on a Samsung air conditioner indicates a fault with the PWM discharge temperature sensor in the outdoor unit. This sensor monitors the refrigerant discharge temperature as it exits the compressor. The control board detects an OPEN or SHORT circuit condition in the sensor circuit, which prevents the system from accurately reading discharge temperatures. This protection is only active when the outdoor ambient temperature is above -10°C, because below that threshold, sensor behavior may be influenced by extreme cold in ways that could generate false readings.

The error thresholds are voltage-based. An OPEN circuit condition is flagged when the sensor signal voltage exceeds 4.95V, which corresponds to a temperature reading below -30°C, indicating the sensor or its wiring has lost continuity. A SHORT circuit condition is flagged when the voltage drops below 0.5V, corresponding to a reading above 151°C, indicating the sensor circuit has been shorted to ground or the sensor element itself has failed in a low-resistance state.

The discharge temperature sensor is a thermistor, meaning its resistance changes predictably with temperature. When the circuit is intact and the sensor is functioning normally, the resistance across the sensor terminals should fall within the expected range for the current ambient conditions. Failures in this circuit are commonly caused by physical damage to the sensor wiring harness, corrosion at the connector, or degradation of the thermistor element itself due to prolonged exposure to high temperatures near the compressor discharge line.

Source: manufacturer service documentation.

Common causes of E407

  1. 01

    Faulty or degraded thermistor sensor

    Part replacement

    The thermistor element itself can fail due to prolonged heat exposure near the compressor discharge line, resulting in either an open or short circuit. Measuring resistance across the sensor terminals will confirm if the reading is outside the expected range for the current temperature.

  2. 02

    Loose or disconnected sensor connector

    Wiring / connection

    Vibration from the outdoor unit can cause the sensor connector to work loose from its socket on the control board or sensor harness. Inspect the connector for secure seating and check for bent or pushed-back pins.

  3. 03

    Corroded or damaged connector terminals

    Wiring / connection

    Moisture ingress into the outdoor unit can corrode the connector terminals, increasing resistance to the point where the control board reads the circuit as open. Look for visible oxidation or green discoloration at the connector.

  4. 04

    Damaged sensor wiring harness

    Part replacement

    The wiring between the sensor and the control board can be pinched, chafed, or broken, especially near routing points or sharp edges in the outdoor cabinet. A visual inspection of the full harness length and a continuity test will identify breaks.

  5. 05

    Failed outdoor unit control board

    Part replacement

    If the sensor and all wiring check out correctly but the error persists, the input circuit on the outdoor control board may have failed, causing it to misread a valid sensor signal as a fault condition.

See the test procedure for each cause

Frequently asked questions about E407

What does E407 mean on a Samsung air conditioner?
E407 indicates a PWM discharge temperature sensor OPEN or SHORT error in the outdoor unit. The control board has detected a sensor signal voltage outside the valid operating range, either above 4.95V (indicating an open circuit, associated with readings below -30°C) or below 0.5V (indicating a short circuit, associated with readings above 151°C). This fault is only triggered when the outdoor temperature is above -10°C.
Can I fix the E407 error myself?
Some basic checks are within reach for a knowledgeable DIYer. You can inspect the sensor connector on the outdoor unit for looseness, corrosion, or visible wiring damage. However, measuring sensor resistance accurately and replacing the thermistor or control board requires access to the outdoor unit's electrical components, so a qualified technician is recommended if the connector inspection does not reveal an obvious issue.
Is it safe to run my air conditioner with an E407 error?
No, you should not attempt to bypass or continue running the system with an active E407 error. The discharge temperature sensor protects the compressor from overheating. Without accurate discharge temperature data, the system cannot prevent compressor damage, which could lead to a much more expensive failure.
How much does it cost to repair an E407 error on a Samsung air conditioner?
Repair costs vary depending on the root cause. If the issue is a loose connector or minor wiring repair, labor costs may be the primary expense, typically in the range of $75 to $150. Replacing the discharge temperature sensor itself usually costs $50 to $150 for parts plus labor. If the outdoor control board has failed, parts and labor combined can range from $300 to $600 or more.
Will resetting the air conditioner clear the E407 error?
A power reset may temporarily clear the error code, but it will return if the underlying sensor or wiring fault has not been corrected. The control board re-evaluates the sensor circuit each time the system runs, so the E407 will reappear as soon as the fault condition is detected again. A reset alone is not a repair.

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