Daewoo Air Conditioner Error Code 1 blink (ON lamp, 0.5s pattern)

The 1 blink (ON lamp, 0.5s pattern) error code on a Daewoo air conditioner signals a fault in one or both of the system's thermistor coil sensors: the indoor coil sensor or the outdoor coil sensor. These sensors are negative temperature coefficient (NTC) thermistors that continuously monitor refrigerant coil temperatures and feed that data to the control board. When the control board detects a resistance reading outside the expected range, indicating either an open circuit (infinite or very high resistance) or a short circuit (near-zero resistance), it locks out operation entirely and triggers this blink pattern on the ON indicator lamp.

An open condition occurs when the thermistor element itself fails internally or when the wiring connection between the sensor and the control board is broken. A short condition occurs when the sensor element fails in the opposite direction, or when damaged wiring creates an unintended low-resistance path. In either case, the control board cannot determine accurate coil temperatures, which prevents it from safely managing compressor cycling, defrost timing, and freeze protection. Because the unit cannot distinguish between an indoor or outdoor sensor fault by this code alone, both sensors and their wiring harnesses must be inspected.

Diagnosis involves disconnecting each coil sensor connector at the control board and measuring resistance across the sensor terminals with a multimeter. A properly functioning NTC thermistor will show a measurable resistance that changes with temperature, typically decreasing as temperature rises. An open sensor will read OL or infinite resistance. A shorted sensor will read near zero ohms. Wiring harness continuity should also be confirmed from sensor plug to board connector to rule out harness faults before replacing sensors.