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Samsung Air Conditioner Error Code E402

Outdoor unit compressor discharge temperature 1 protection control.

Samsung codesSamsung air conditioner codes

Outdoor unit compressor discharge temperature 1 protection control.

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What E402 means on a Samsung air conditioner

The E402 error code on a Samsung air conditioner indicates that the outdoor unit's compressor discharge temperature sensor 1 has detected a temperature that exceeds the safe operating threshold, triggering a protection control response. The discharge temperature refers to the temperature of the refrigerant gas as it exits the compressor at high pressure. This is one of the most thermally stressed points in the refrigeration cycle, and Samsung's control board continuously monitors this value to prevent compressor damage from overheating.

When discharge temperatures climb too high, the compressor windings and internal components face accelerated wear, oil breakdown, and potential mechanical failure. Common triggers include low refrigerant charge, which forces the compressor to work harder and reduces the cooling effect on discharge gas. Blocked airflow across the condenser coil, a failing condenser fan motor, or operating in extremely high ambient temperatures can also cause discharge temps to spike. A faulty discharge temperature sensor itself may send a false high-temperature signal even when actual temperatures are within range.

When E402 activates, the system enters a protection mode, typically shutting down or limiting compressor operation to prevent hardware damage. Technicians should check refrigerant pressure, inspect the condenser coil for debris or fouling, verify the condenser fan is operating at correct speed, and test the discharge temperature sensor for proper resistance values before assuming a refrigerant or compressor issue.

Source: manufacturer service documentation.

Common causes of E402

  1. 01

    Low refrigerant charge

    Part replacement

    Insufficient refrigerant causes the compressor to work harder without adequate cooling of the discharge gas, rapidly raising discharge temperatures. A technician can confirm this by checking system pressures with a manifold gauge set.

  2. 02

    Blocked or dirty condenser coil

    Wiring / connection

    Debris, dirt, or vegetation restricting airflow through the outdoor condenser coil reduces heat dissipation and causes discharge temperatures to rise. Inspect the coil visually and clean it if fouling is present.

  3. 03

    Condenser fan motor failure or reduced speed

    Part replacement

    If the condenser fan is not moving sufficient air across the coil, heat cannot be rejected efficiently and compressor discharge temps will climb. Check that the fan spins freely, runs at full speed, and draws correct amperage.

  4. 04

    Faulty discharge temperature sensor

    Part replacement

    A defective sensor can report falsely elevated temperatures and trigger E402 even when the compressor is operating normally. Test the sensor's resistance value and compare it against the specification for the unit's operating temperature range.

  5. 05

    Extremely high ambient temperature or restricted installation clearance

    Wiring / connection

    Operating in ambient temperatures beyond the unit's design limits, or installing the outdoor unit in a confined space without adequate clearance, can push discharge temps into the protection range. Verify the installation meets Samsung's minimum clearance requirements.

See the test procedure for each cause

Frequently asked questions about E402

What does E402 mean on a Samsung air conditioner?
E402 indicates that the outdoor unit's compressor discharge temperature sensor 1 has detected an overtemperature condition, triggering a protection control shutdown. The system is designed to stop compressor operation before heat-related damage can occur. This code points to an issue with heat rejection in the outdoor unit, the refrigerant charge level, or possibly the sensor itself.
Can I fix E402 on my Samsung air conditioner myself?
Some basic checks are within reach for a homeowner, such as clearing debris from around the outdoor unit, cleaning a visibly dirty condenser coil, and ensuring nothing is blocking airflow. However, diagnosing low refrigerant, testing the discharge temperature sensor, or inspecting the condenser fan motor properly requires tools and training. A licensed HVAC technician should be called if basic clearing steps do not resolve the error.
Is it safe to keep running my Samsung air conditioner with an E402 error?
No. The E402 code triggers a protection shutdown specifically to prevent compressor damage from excessive heat. Bypassing or repeatedly resetting the unit without addressing the root cause risks permanent compressor failure, which is a much more costly repair. The system should remain off until the underlying issue is diagnosed and corrected.
Will resetting my Samsung air conditioner clear the E402 error?
A power reset may temporarily clear the error and allow the unit to restart, but if the underlying cause is not fixed, the E402 code will return, often quickly. Repeated high-temperature events can shorten compressor life significantly. A reset should only be used as part of a diagnostic process, not as a long-term solution.
How much does it cost to repair a Samsung air conditioner showing E402?
Repair costs depend heavily on the root cause. Cleaning the condenser coil or clearing airflow obstructions may involve only a service call fee, typically in the range of $75 to $150. Refrigerant recharge can cost $150 to $400 or more depending on refrigerant type and the amount needed. Condenser fan motor replacement generally runs $150 to $350 in parts and labor, while a full compressor replacement can range from $600 to $1,500 or higher depending on the unit.

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