mypros+
Error code reference

Samsung Air Conditioner Error Code E423

SUMP TEMP FIXED 3 sensor OPEN/SHORT error. Detected when outdoor temp over -10°C. Error level

Samsung codesSamsung air conditioner codes

SUMP TEMP FIXED 3 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.

MyPros+ Max

Get the full diagnostic procedure for E423.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What E423 means on a Samsung air conditioner

The E423 error code on a Samsung air conditioner indicates a fault with the SUMP TEMP FIXED 3 sensor, specifically an open or short circuit condition. This sensor monitors temperature in the sump region of the outdoor unit and is active when the outdoor ambient temperature is above -10°C. The control board flags the fault when the sensor signal voltage reads above 4.95V, which corresponds to a temperature reading below -30°C and indicates an open circuit condition, or when the voltage drops below 0.5V, corresponding to a temperature above 151°C and indicating a short circuit condition. Either condition places the sensor reading outside its valid operating range, triggering the error.

The SUMP TEMP FIXED 3 sensor is a negative temperature coefficient (NTC) thermistor. As temperature rises, resistance falls, which in turn lowers the voltage signal read by the control board. An open circuit, caused by a broken wire or a failed sensor body, drives the signal voltage artificially high. A short circuit, caused by damaged insulation or a connector fault, collapses the voltage below the acceptable threshold. Both conditions prevent the system from accurately monitoring sump temperature, which is critical for protecting compressor operation and managing refrigerant levels.

Diagnosis begins at the sensor connector. Inspect the connector for corrosion, bent pins, or loose seating. With the connector separated and power off, measure resistance across both sensor terminals using a multimeter. An open circuit will read infinite resistance, while a short circuit will read near zero ohms. A healthy NTC thermistor will show a finite resistance value that changes with temperature. If the connector checks out, inspect the wiring harness between the sensor and the control board for chafing, pinching, or moisture intrusion.

Source: manufacturer service documentation.

Common causes of E423

  1. 01

    Faulty or failed sensor

    Part replacement

    The NTC thermistor itself may have failed internally, producing either infinite resistance (open) or near-zero resistance (short). This is the most frequent root cause and will require sensor replacement.

  2. 02

    Damaged or disconnected sensor connector

    Wiring / connection

    The connector at the sensor or control board may be loose, corroded, or have bent pins that interrupt the signal. Inspect and reseat both ends of the connector as the first physical check.

  3. 03

    Wiring harness damage

    Wiring / connection

    The wire between the sensor and the control board may be chafed, pinched, or broken, especially where it routes near sharp metal edges or moving components. A continuity test along the harness will confirm this.

  4. 04

    Moisture intrusion at connector or sensor body

    Wiring / connection

    Water ingress into the connector housing can cause short circuits or accelerated corrosion that degrades the signal. Look for evidence of rust, green oxidation, or water tracks on the connector and sensor housing.

  5. 05

    Control board fault

    Part replacement

    If the sensor, connector, and wiring all test within normal parameters, the input circuit on the control board may be defective, causing it to misread a valid sensor signal. This is the least likely cause and should be ruled out last.

See the test procedure for each cause

Frequently asked questions about E423

What does E423 mean on a Samsung air conditioner?
E423 indicates an open or short circuit fault on the SUMP TEMP FIXED 3 sensor in the outdoor unit. The error triggers when the sensor voltage rises above 4.95V or drops below 0.5V, placing it outside the valid measurement range. This sensor monitors sump temperature and is only active when outdoor temperatures are above -10°C. The fault can be caused by a failed sensor, a damaged connector, or a wiring harness issue.
Can I fix the E423 error myself?
A knowledgeable DIYer can perform the initial diagnostic steps, including inspecting the sensor connector and measuring resistance across the sensor terminals with a multimeter. If the sensor reads open or short, replacing the thermistor is a relatively straightforward task. However, if the fault traces back to the control board, professional service is recommended.
Is it safe to run my Samsung air conditioner with an E423 error?
Continuing to operate the unit with an active E423 fault is not advisable. The sump temperature sensor helps protect the compressor and manage refrigerant behavior. Running the system without a valid sensor reading can lead to compressor damage or reduced efficiency. It is best to resolve the fault before resuming normal operation.
How much will it cost to repair an E423 error?
If only the sensor needs replacement, repair costs typically fall in the range of $75 to $200, depending on labor rates and part availability. If the control board is the root cause, costs can rise to the range of $250 to $600 or more. Getting a diagnosis first will help narrow down the scope of the repair.
Will resetting my Samsung air conditioner clear the E423 error?
A power reset may temporarily clear the error code from the display, but the fault will return if the underlying hardware problem is not corrected. The control board will detect the out-of-range sensor signal again once the unit restarts and outdoor temperatures are above -10°C. A permanent fix requires identifying and repairing or replacing the defective component.

Related Samsung air conditioner codes

All Samsung air conditioner codes
View all 572 Samsung air conditioner codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass