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Error code reference

Samsung Air Conditioner Error Code E191

Pipe test error

Samsung codesSamsung air conditioner codes

Pipe test error - no temperature difference in EVA_OUT or temperature changes in incorrect indoor unit EVA_OUT.

First step from the service manual

Check if the indoor unit ADDRESS is same as the set ADDRESS on MCU; check the MCU indoor unit setting switch.

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

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What E191 means on a Samsung air conditioner

The E191 error code on a Samsung air conditioner indicates a pipe test error, specifically related to the EVA_OUT (evaporator outlet) temperature sensor circuit during system commissioning or auto-addressing routines. During a pipe test, the system verifies that each indoor unit is responding correctly by monitoring temperature changes at its evaporator outlet. If the EVA_OUT temperature shows no change when refrigerant flow is expected, or if temperature changes are detected at the wrong indoor unit's EVA_OUT sensor, the system flags E191. This points to a mismatch between how the indoor units are addressed and how the control system expects them to be mapped.

The root cause is most commonly an address conflict or misconfiguration between the indoor unit's physical address setting and the address stored in or assigned by the MCU (main control unit). Samsung multi-zone systems use address switches on the indoor unit PCBs to assign each unit a unique position in the system. If these switch settings do not match the MCU's expected configuration, the pipe test cannot correctly attribute temperature data to the right unit, resulting in the E191 fault. This can occur after replacing a PCB, rewiring communication lines, or during initial installation if the address switches were not set correctly.

Diagnosis should begin by comparing the address set on the indoor unit's physical address switch with the address registered on the MCU. If these do not match, correcting the switch setting or updating the MCU configuration should resolve the fault. Beyond addressing, the EVA_OUT temperature sensor itself and its wiring should also be inspected, as a failed or disconnected sensor would prevent the system from detecting the expected temperature differential during the pipe test.

Source: manufacturer service documentation.

Common causes of E191

  1. 01

    Indoor unit address mismatch with MCU

    Wiring / connection

    The address set on the indoor unit's PCB switch does not match the address configured on the MCU. This is the primary cause and is confirmed by comparing the physical address switch position on the indoor unit against the MCU's registered address for that unit.

  2. 02

    Incorrect MCU indoor unit setting switch configuration

    Wiring / connection

    The MCU's indoor unit setting switch may be configured for a different number of units or a different address range than what is physically installed. Reviewing and correcting the MCU switch settings is a key diagnostic step.

  3. 03

    Faulty or disconnected EVA_OUT temperature sensor

    Part replacement

    If the evaporator outlet temperature sensor is unplugged, damaged, or has failed, the system will not detect any temperature change during the pipe test, triggering E191. Inspect the sensor connector and wiring at the indoor unit PCB.

  4. 04

    Communication wiring error between indoor units

    Wiring / connection

    Crossed or improperly connected communication cables can cause the system to attribute temperature readings to the wrong indoor unit. Verify that each indoor unit's communication wiring corresponds to its assigned address.

  5. 05

    Indoor unit PCB replacement without address re-configuration

    Wiring / connection

    After a PCB replacement, the address switch on the new board may default to a different position than the original. If the address was not reconfigured after the swap, E191 can result. Check and reset the address switch to match the system layout.

See the test procedure for each cause

Frequently asked questions about E191

What does E191 mean on a Samsung air conditioner?
E191 indicates a pipe test error involving the EVA_OUT (evaporator outlet) temperature sensor on one or more indoor units. The system either detected no temperature change at the expected indoor unit's EVA_OUT during a pipe test, or detected a change at the wrong unit. This points to an address mismatch between the indoor unit and the MCU, or a sensor-related fault.
How do I fix the E191 error on my Samsung air conditioner?
Start by checking that the address switch on each indoor unit's PCB matches the address assigned on the MCU. If there is a mismatch, correct the switch setting and re-run the pipe test. Also inspect the EVA_OUT temperature sensor and its wiring for damage or disconnection. If the error persists after addressing corrections, a qualified technician should inspect the communication wiring and MCU configuration.
Is the E191 error on a Samsung air conditioner dangerous?
The E191 error is not a safety-critical fault in the sense of an electrical hazard, but it does indicate the system cannot properly verify refrigerant distribution across indoor units. Operating the system long-term with this fault unresolved could result in uneven cooling, potential compressor stress, or other performance issues. It is best to have the error diagnosed and corrected promptly.
Will resetting my Samsung air conditioner clear the E191 error?
A simple power reset is unlikely to permanently clear E191 because the underlying cause is a configuration or hardware issue rather than a temporary communication glitch. The error will typically return when the system runs its pipe test again. The root cause, usually an address mismatch or sensor fault, must be corrected before the code will clear reliably.
How much does it cost to repair an E191 error on a Samsung air conditioner?
If the fix is a simple address switch reconfiguration, labor costs from a technician visit may range from around $75 to $200 depending on your location and service provider. If the EVA_OUT temperature sensor needs replacement, parts can add an additional $20 to $80 or more. If a PCB replacement is required, total repair costs could range from $200 to $600 or higher. Getting a diagnostic quote from a Samsung-authorized technician is recommended.

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