Samsung Air Conditioner Error Code E173

Error code E173 on a Samsung air conditioner indicates that the evaporator outlet (EVAP OUT) temperature sensor on a separate indoor unit detected an unexpected temperature change during the piping check sequence. The piping check is an automated commissioning procedure used in multi-split systems to verify that refrigerant is flowing correctly through each indoor unit's piping circuit. During this process, each unit is cycled and monitored for temperature response. If the system detects a temperature shift at the EVAP OUT sensor of a different indoor unit than the one currently being tested, it flags E173 because that cross-response suggests a refrigerant routing problem or an addressing conflict between units.

The most common root causes fall into three categories: indoor unit address mismatches, Electronic Expansion Valve (EEV) faults, and physical piping errors. In a multi-split installation, each indoor unit must have a unique address that matches its MCU (Main Control Unit) configuration. If two units share an address or an address is incorrectly assigned, the system cannot correctly attribute temperature readings to the right unit, triggering this error. An EEV that is stuck open or not responding to control signals can allow refrigerant to flow into the wrong circuit during the piping check, causing an unintended temperature change at the wrong unit's sensor.

Physical piping connection errors, such as liquid and suction lines swapped between indoor units, can also produce this fault. During the piping check, the system expects a defined temperature response from a specific unit. If refrigerant is routed incorrectly due to crossed connections, the EVAP OUT sensor on an adjacent unit registers the change instead. Technicians should confirm address DIP switch or software settings, inspect EEV wiring harnesses and coil resistance, and trace refrigerant piping back to the outdoor unit to rule out crossed connections before clearing and rerunning the piping check.