Daewoo Air Conditioner Error Code ON LAMP Blink (continuous)

The continuous blinking of the ON lamp on a Daewoo air conditioner indicates a fault detected in the room temperature thermistor circuit. This thermistor is a negative temperature coefficient (NTC) resistor located in the indoor unit, typically positioned in the return air path to measure the ambient room temperature. The control board monitors the resistance value of this sensor to regulate cooling output and compressor operation. When the board detects a resistance value outside the expected range, either an open circuit (infinite resistance) or a short circuit (near-zero resistance), it triggers the continuous ON lamp blink fault signal.

Despite the fault condition, the unit does not shut down entirely. Instead, it enters a failsafe mode in which it continues operating with the room temperature reading fixed at 32 degrees Celsius. In cooling mode, this fixed value causes the unit to run continuously since the assumed room temperature remains above any reasonable setpoint. While this allows some continued cooling function, temperature regulation is no longer accurate and the unit will not cycle correctly based on actual room conditions.

The most common causes include thermistor degradation due to age or moisture exposure, physical damage to the sensor or its wiring harness, and corroded or loose connector pins at the control board. Diagnosis begins with measuring the thermistor resistance directly at the sensor leads and comparing the value to the expected resistance curve for the ambient temperature. A reading of zero ohms confirms a short, while an open line will show no continuity. Inspecting the wiring harness for breaks, pinch points, or connector corrosion is also essential before condemning the sensor itself.