Samsung Heat Pump Error Code E603

E603 is an indoor unit electronic expansion valve (EEV) close error, specifically flagged on the second detection attempt. It means the indoor PCB commanded the EEV to open, but the valve did not move as expected on two consecutive checks. The system logs this fault to prevent improper refrigerant metering, which could damage the compressor or reduce system efficiency.

A power reset may temporarily clear the fault if it was triggered by a transient wiring issue or signal anomaly, but E603 is a second-detection fault, meaning the system already confirmed the problem twice before logging it. If the underlying cause, such as a bad EEV coil, stuck valve, or wiring fault, is not corrected, the error will return promptly after the system restarts and attempts normal operation.

Repair costs depend on what component has failed. If the issue is simply a loose wiring connector, the cost may be limited to a service call fee, typically in the range of $75 to $150. If the EEV coil or valve body requires replacement, parts and labor combined can range from $200 to $600 or more depending on the unit model and local labor rates. A PCB replacement, if required, can push costs higher.

A homeowner can safely check that the EEV wiring connector is fully plugged in at the indoor unit PCB, since this is the first recommended diagnostic step. However, any further diagnosis involving refrigerant-side components, coil resistance testing, or PCB evaluation should be performed by a qualified HVAC technician. Working on refrigerant circuits requires proper certification and equipment.

You should not continue operating the system with an active E603 error. A non-functioning EEV means refrigerant flow to the indoor coil is not being properly regulated, which can cause liquid refrigerant slugging, compressor damage, or loss of effective heating and cooling capacity. The system should remain off until the fault is diagnosed and repaired.