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Error code reference

Samsung Air Conditioner Error Code 291

High pressure sensor error (Open/Short)

Samsung codesSamsung air conditioner codes

High pressure sensor error (Open/Short) - short error below 0.4V, open error over 4.2V.

First step from the service manual

Check wire breaking of high pressure sensor; check high pressure sensor circuit and sensor.

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

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What 291 means on a Samsung air conditioner

Samsung air conditioner error code 291 indicates a fault detected in the high pressure sensor circuit. The high pressure sensor monitors refrigerant pressure on the discharge side of the compressor, and the control board uses its voltage output to determine whether system pressure is within safe operating limits. The error triggers under two specific electrical conditions: a short circuit, where the sensor signal voltage drops below 0.4V, or an open circuit, where the voltage rises above 4.2V. Either condition causes the board to interpret the signal as invalid and halt normal operation to prevent potential compressor or refrigerant system damage.

The high pressure sensor is a transducer that converts refrigerant pressure into a variable voltage signal read by the main PCB. Under normal operation, the output voltage stays within a defined range between these threshold values. When wiring to the sensor is broken, pinched, or corroded, the circuit can read as open (above 4.2V). A shorted sensor, damaged connector, or failed sensor element itself can pull the signal voltage below 0.4V, triggering the short error condition. Both scenarios produce code 291 but point to different root causes.

Diagnosis should begin with a physical inspection of the high pressure sensor wiring harness, checking for broken conductors, loose connector pins, corrosion, or insulation damage. After confirming wiring integrity, the sensor itself should be tested for correct voltage output and compared against expected operating values. If wiring is intact and the sensor output is out of range under normal system conditions, sensor replacement is likely required. The refrigerant circuit should also be evaluated, as an actual high pressure condition can sometimes stress or damage the sensor.

Source: manufacturer service documentation.

Common causes of 291

  1. 01

    Broken or damaged sensor wiring

    Wiring / connection

    A broken wire in the high pressure sensor harness is the most common cause of this error. Inspect the full wiring run from the sensor connector to the control board for cuts, pinches, or pulled terminals that would interrupt the signal circuit.

  2. 02

    Loose or corroded connector

    Wiring / connection

    A corroded or poorly seated connector at the sensor or PCB end can cause an intermittent or complete loss of signal, producing either an open or short reading. Disconnect and inspect all connectors in the high pressure sensor circuit for oxidation or bent pins.

  3. 03

    Failed high pressure sensor

    Part replacement

    If the wiring and connectors check out correctly, the sensor transducer itself may have failed internally, causing its output to fall outside the 0.4V to 4.2V acceptable range. A failed sensor will need to be replaced to restore normal operation.

  4. 04

    Short circuit in sensor wiring

    Wiring / connection

    Chafed or pinched insulation can allow the signal wire to contact ground, pulling the sensor voltage below the 0.4V short-error threshold. Trace the harness carefully along any areas where it contacts sheet metal edges or other components.

  5. 05

    Control board input circuit fault

    Part replacement

    In less common cases, the PCB sensor input circuit itself may be damaged, causing it to misread an otherwise functional sensor signal. This should be considered only after the wiring and sensor have been confirmed as good.

See the test procedure for each cause

Frequently asked questions about 291

What does 291 mean on a Samsung air conditioner?
Error code 291 on a Samsung air conditioner indicates a high pressure sensor error caused by an open or short circuit condition. A short error occurs when the sensor signal voltage drops below 0.4V, and an open error occurs when the voltage exceeds 4.2V. The unit stops operating to protect the refrigerant system and compressor. The fault is most often related to wiring, connector, or sensor issues rather than an actual refrigerant pressure problem.
Can I fix error code 291 myself?
Some basic checks are within reach for a knowledgeable DIYer, such as inspecting the high pressure sensor wiring harness for obvious breaks, loose connectors, or corrosion. However, testing the sensor output voltage and working around refrigerant system components generally requires proper tools and technical knowledge. If wiring inspection does not resolve the issue, a qualified HVAC technician should complete the diagnosis and repair.
Is it safe to run my Samsung air conditioner with error code 291?
No, you should not continue operating the unit while error code 291 is active. The high pressure sensor protects the compressor and refrigerant circuit from dangerous over-pressure conditions. With the sensor circuit faulted, the system cannot monitor pressure reliably, which removes an important safety safeguard. Keep the unit off until the fault is diagnosed and repaired.
How much does it cost to repair a Samsung air conditioner error code 291?
Repair costs vary depending on whether the fix involves only wiring or connector work versus sensor or control board replacement. Wiring repairs and connector cleaning are typically lower cost, often in the range of $75 to $200 for labor. High pressure sensor replacement, including parts and labor, generally falls in the $150 to $400 range. Control board replacement, if required, can be more expensive depending on the model.
Will resetting my Samsung air conditioner clear error code 291?
A power reset may temporarily clear the error from the display, but the code will return if the underlying wiring or sensor fault is still present. Because the error is caused by an electrical circuit condition rather than a temporary operating glitch, resetting the unit does not fix the problem. A proper diagnosis of the high pressure sensor circuit is needed before the error will stay cleared.

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