Samsung Air Conditioner Error Code E403

E403 indicates the system has detected suction-side refrigerant pressure below the minimum required threshold before pump down start. Specifically, the low pressure sensor read below 3.1 kg/cm2G during cooling or below 2.6 kg/cm2G during heating for 3 consecutive seconds. The control board blocks the compressor from starting to prevent mechanical damage. The fault points to either a low refrigerant charge or a problem with the pressure sensor itself.

No. The E403 fault is a protective lockout that prevents the compressor from starting specifically because running on low refrigerant pressure can cause severe compressor damage. The unit will refuse to operate normally until the fault condition is resolved. Attempting to override the lockout or repeatedly resetting the unit without addressing the root cause risks costly compressor failure.

A power reset may temporarily clear the fault display, but E403 will return immediately if the underlying pressure condition still exists. Because the sensor continuously monitors suction pressure and the fault triggers within 3 seconds of the threshold being breached, the lockout will reactivate as soon as the system attempts to start. A reset is only a valid resolution after the actual cause, whether a refrigerant leak, faulty sensor, or restriction, has been diagnosed and corrected.

Some basic checks, such as inspecting wiring to the low pressure sensor and verifying the sensor connector is secure, can be done without special tools. However, diagnosing and correcting low refrigerant pressure requires a manifold gauge set and EPA certification to handle refrigerants legally. If the system has lost refrigerant due to a leak, a certified HVAC technician must locate the leak, repair it, and recharge the system.

Repair costs vary widely depending on the root cause. A sensor replacement typically runs in the range of $100 to $250 including labor. If the system needs a leak repair and refrigerant recharge, costs commonly range from $200 to $600 or more depending on the leak location, refrigerant type, and quantity required. A blocked expansion valve or filter drier replacement will generally fall in the $150 to $400 range for parts and labor.