Why does BMW air conditioning not cool in auto mode but works normally in manual mode?
2 Answers
BMW air conditioning not cooling in auto mode but working normally in manual mode is due to the following reasons: insufficient refrigerant in the air conditioning system; the refrigerant pressure switch detects low pressure or the pressure switch is faulty; the air conditioning compressor is faulty; the air conditioning function switch is faulty. How air conditioning works: The air conditioning system compresses gaseous refrigerant into high-temperature, high-pressure gas through the compressor, which then flows through the pipes into the condenser. In the condenser, the refrigerant is cooled and condensed into high-pressure liquid refrigerant through heat dissipation by the cooling fan. The high-pressure liquid refrigerant then enters the dryer reservoir through the pipes, where it undergoes a rapid state change, turning into low-temperature, low-pressure liquid refrigerant that enters the evaporator. In the evaporator, it absorbs heat from the air flowing through it, lowering the air temperature and blowing out cold air, thereby producing a cooling effect. Refrigerant working process: The refrigerant continuously circulates in the air conditioning system to produce a cooling effect; when the compressor stops working, the refrigerant in the air conditioning system stops flowing, and no cooling effect is produced.
I've been driving a BMW for several years and recently encountered the same issue where the air conditioning didn't cool in auto mode but worked fine in manual mode. It was quite annoying. Generally, auto mode relies on the coordination between the in-car temperature sensor and the air conditioning control unit, while manual mode directly activates the compressor. After getting my car checked, it turned out that dust accumulation on the temperature sensor caused inaccurate readings, leading the auto mode to mistakenly assume cooling wasn't needed. I cleaned the sensor location myself—it's near the center console—and the function was restored afterward. Additionally, this problem tends to occur more often in hot weather, so it's advisable to regularly clean the air conditioning system to prevent blockages from dirt. If the issue persists, it might be a software bug in the control unit, which a dealership can fix by updating the program. Don't ignore this—safety comes first, especially in summer driving.
