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Error code reference

Samsung Air Conditioner Error Code E155

Mixed operation error (operating heat and cool mode at same time).

Samsung codesSamsung air conditioner codes

Mixed operation error (operating heat and cool mode at same time).

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What E155 means on a Samsung air conditioner

The E155 error code on a Samsung air conditioner indicates a mixed operation error, which occurs when the system attempts to run heating and cooling modes simultaneously. In a standard split or multi-split system, the refrigerant circuit is designed to operate in one direction at a time, either absorbing heat from the indoor space and rejecting it outdoors (cooling) or reversing that flow to bring heat indoors (heating). When control signals conflict and both modes are commanded at the same time, the system detects the contradiction and triggers E155 to prevent mechanical and refrigerant circuit damage.

This condition most commonly arises in multi-zone systems where individual indoor units are set to different operating modes. Samsung multi-split systems typically require all connected indoor units to operate in the same mode, either all cooling or all heating, because they share a single outdoor refrigerant circuit. If one zone calls for cooling while another calls for heating, the outdoor unit receives conflicting demands and cannot satisfy both simultaneously, resulting in the E155 fault.

The error can also stem from a fault in the communication wiring between indoor and outdoor units, a malfunctioning main control board that is sending incorrect mode signals, or corrupted settings stored in the system memory. In some cases, a simple power cycle clears a transient communication glitch that caused the mixed mode signal. However, if the error returns consistently, the control board, wiring harness, or mode selector circuit will need to be inspected more thoroughly.

Source: manufacturer service documentation.

Common causes of E155

  1. 01

    Conflicting mode settings across multiple indoor zones

    Wiring / connection

    In multi-split systems, if one indoor unit is set to cool while another is set to heat, the shared outdoor unit cannot comply with both. Check that all indoor units are set to the same operating mode.

  2. 02

    Communication wiring fault between indoor and outdoor units

    Wiring / connection

    Damaged, loose, or incorrectly connected communication cables can cause garbled mode signals, making the outdoor unit interpret simultaneous heating and cooling requests. Inspect the signal wiring and connectors at both ends for damage or poor contact.

  3. 03

    Faulty main control board on the indoor or outdoor unit

    Part replacement

    A defective control board may send incorrect or conflicting mode commands even when the user setting is correct. If the error persists after verifying zone settings and wiring, the control board is a likely culprit and will need replacement.

  4. 04

    Corrupted system memory or settings

    Wiring / connection

    A power surge or interrupted firmware update can corrupt stored operating parameters, causing the system to register an invalid mode state. A full power reset, cutting power at the breaker for several minutes, can sometimes clear this condition.

  5. 05

    Faulty mode selector or remote control sending incorrect signals

    Part replacement

    A malfunctioning remote control or wall controller that repeatedly sends both heat and cool commands can trigger this error. Test with a replacement remote or the Samsung SmartThings app to rule out a controller hardware issue.

See the test procedure for each cause

Frequently asked questions about E155

What does E155 mean on a Samsung air conditioner?
E155 is a mixed operation error, meaning the system has detected simultaneous commands to run both heating and cooling modes at the same time. This is not a physically possible operating state for a single refrigerant circuit, so the system faults out to protect itself. It is most common in multi-zone systems where different indoor units are set to different modes.
Can I fix the E155 error myself without a technician?
In many cases, yes. Start by checking that all indoor units in your system are set to the same mode, either all cooling or all heating, not a mix of both. If the settings look correct, cut power to the system at the circuit breaker for five to ten minutes and restart. If the error clears and does not return, the cause was likely a temporary communication glitch. If it comes back, a technician should inspect the wiring and control boards.
Is the E155 error dangerous, and can I keep using the air conditioner?
The E155 error is a protective fault, not a safety hazard in the way that a gas or electrical failure would be. The system shuts itself down rather than operating in a conflicting state, which is the correct response. You should not attempt to bypass or ignore the error, as forcing the unit to run with conflicting mode signals could stress the compressor and refrigerant circuit over time.
Will resetting the unit clear the E155 error on a Samsung air conditioner?
A power reset, turning the breaker off and back on after several minutes, can clear E155 if the cause was a temporary communication error or corrupted setting. However, if an underlying issue such as conflicting zone settings, damaged wiring, or a faulty control board is present, the error will return after the reset. Always address the root cause rather than relying on repeated resets.
How much does it cost to repair an E155 error on a Samsung air conditioner?
Repair costs depend heavily on the root cause. If the fix is simply correcting zone mode settings, there is no parts cost and a service call fee of roughly $75 to $150 may be all you pay. If communication wiring needs repair or replacement, expect $100 to $300 in parts and labor. A main control board replacement, which is the most expensive scenario, typically runs $200 to $600 or more depending on the model and labor rates in your area.

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