Samsung Air Conditioner Error Code E558

Error code E558 on a Samsung air conditioner indicates a persistent Electronic Expansion Valve (EEV) open fault, classified as a second detection event. The EEV is a precision-controlled valve that regulates refrigerant flow into the indoor unit by modulating its opening position in response to signals from the indoor PCB. When the system detects that the EEV is stuck in or defaulting to an open position and cannot be commanded closed, refrigerant continues flowing into a unit that has stopped operating. This condition is flagged as E558 after the failure has been detected a second time, indicating the fault is not intermittent but persistent.

A refrigerant leak into a stopped indoor unit creates several downstream problems. With the blower not running, the heat exchange coil can develop ice buildup from unregulated refrigerant flow, and system pressures across the entire refrigerant circuit can become imbalanced. The EEV itself is a motorized stepper valve driven by a dedicated coil assembly connected directly to the indoor unit PCB. If the valve coil loses continuity, the connector is loose or corroded, or the PCB driver circuit fails, the controller loses the ability to command the valve closed and registers the open fault.

Diagnosis begins at the EEV wiring harness connection on the indoor PCB, as a loose or improperly seated connector is among the most common triggers. If the wiring checks out, the EEV coil resistance should be measured and compared against specification, and the PCB should be inspected for visible damage. Because this is a second-detection fault, the underlying condition has already persisted through one reset cycle, meaning a simple power cycle is unlikely to clear the code without correcting the root cause.