A method for addressing and detecting a fault in an undercooling tube set (400) of an air conditioner. While an air conditioner is performing heating, determine whether a time required to stabilize an exhaust temperature is less than a first preset time (S406). If the time required to stabilize the exhaust temperature is less than the first preset time, then it is possible to confirm that a one-way valve (430) is faulty (S408). In order to further confirm whether the one-way valve (430) is faulty, a main control device (500) further calculates the difference between the stable exhaust temperature and a coil temperature of a heat exchanger (300) in an indoor unit, and compares the difference with a first preset temperature difference (S412). If the difference between the exhaust temperature and the coil temperature is less than the first preset temperature difference, then it is confirmed that the one-way valve (430) is faulty (S414). The method uses the required time to stabilize the exhaust temperature of a test compressor (100) and the difference between the stable exhaust temperature and the coil temperature of the heat exchanger (300) in the indoor unit to accurately determine whether the one-way valve (430) in the undercooling tube set (400) is faulty, thereby addressing the faulty one-way valve (430) in a timely manner and preventing a fault from impacting heating effects of the air-conditioner.