Is It Normal for the BMW 3 Series Air Conditioning Compressor Not to Shut Off?

[DeNevaeh]

Air conditioning compressor not shutting off could be due to setting issues or air conditioning damage. Reasons for the air conditioning compressor not shutting off: The car's air conditioning temperature is set too low, causing the compressor not to shut off. A faulty temperature sensor leads to the compressor not shutting off. The internal computer board thermostat of the air conditioning unit is broken, causing the compressor not to shut off. A refrigerant leak in the air conditioning refrigeration system results in insufficient cooling, causing the compressor not to shut off. Solutions: If the refrigeration system works normally after turning on the air conditioning, then the fault is likely a thermostat malfunction, and the thermostat system should be checked. First, check if the temperature sensing tube connected to the thermostat has fallen off; if so, it should be fixed back to its original position. Secondly, after prolonged use, the internal contacts of the thermostat may become sintered, the control fluid inside the thermostat may leak, or the thermistor of the electronic thermostat may change value. If the cooling effect is poor, it might be due to refrigerant leakage in the air conditioning system, causing the residual refrigerant to fall below the standard cooling capacity. As a result, the resistance value of the thermistor does not meet the required value, so the air conditioning will not shut off.

[JaydenLynn]

As an owner of an older 3 Series for six years, the issue of the compressor not shutting off depends on the situation. It's quite normal for it to run continuously for 20 minutes when starting the AC after parking in the sun during summer, as the cabin is like a big steamer. However, if it doesn't stop even after driving for over an hour, like when the vent temperature stabilizes around 8 degrees Celsius on the highway, the compressor should take intermittent breaks. I encountered a similar issue last week and found it was due to a slight refrigerant leak causing insufficient pressure, forcing the compressor to work overtime. I recommend checking the AC pipes—if the low-pressure pipe is frosted or the airflow from the vents weakens accompanied by a hissing sound, it's likely time to top up the refrigerant. This common issue in older BMWs isn't expensive to fix.

[McJoy]

After playing with cars for over a decade, I've noticed that German cars have different air conditioning logic compared to Japanese cars. The BMW 3 Series' variable displacement compressor adjusts its power based on temperature sensors, typically maintaining low-speed operation rather than shutting off completely. But here's a simple way to check: drive at night with the AC on, set the temperature to the lowest LO setting. If the compressor runs non-stop like crazy for more than five minutes, there's definitely an issue. Focus on checking the AC pressure switch and evaporator temperature sensor—failure of these components can cause the ECU to misjudge cabin temperature. I remember my buddy's F35 had its compressor running non-stop because mice chewed through the sensor wiring harness.

[DeGavin]

Girls driving cars are most afraid of weak air conditioning, and my G20 had a similar issue before. The salesperson said the automatic AC would adjust itself once reaching the set temperature, but last July, I noticed the compressor kept buzzing. After connecting the diagnostic tool at the 4S shop, it turned out the condenser was completely clogged with poplar fluff. The mechanic explained poor heat dissipation could cause the high-pressure pipeline to overheat, forcing the compressor to work at full capacity. Now, every year before summer, I use a high-pressure water gun to clean the radiator gaps. A special reminder for sisters who often drive in areas with lots of willow catkins: watch out for this hidden killer. If you smell a musty sour odor from the AC, be extra cautious.

[DelaneyAnn]

When repairing BMW air conditioning systems for over a decade, there are three key points to focus on if the compressor won't shut off. First, check the outside temperature displayed on the instrument cluster - continuous operation is normal when it's above 35°C. Second, pay attention to the auto start-stop function; when the engine restarts at traffic lights, the compressor needs to rebuild pressure. Third, voltage fluctuations from the alternator - a common issue in older N20 engines - can cause abnormal electromagnetic clutch engagement. A classic case: a customer complained about the compressor not shutting off, which turned out to be caused by an aftermarket subwoofer interfering with CAN bus signals. It's recommended to start with basic troubleshooting, such as switching to ECO mode and driving for half an hour before rechecking.

[VonCody]

As a ride-hailing driver who frequently takes long-distance trips, I'm very familiar with the 3 Series' air conditioning. If the compressor won't shut off, it's probably due to a clogged cabin air filter. Last month when I drove to Inner Mongolia, the airflow dropped by half after a sandstorm - the compressor was working overtime but couldn't cool effectively. An 80-yuan filter replacement fixed it immediately. Another tip: don't set automatic AC temperature too low, around 22°C is optimal. If you notice the temperature gauge rising on highways accompanied by strange AC smells, pull over immediately - this could indicate cooling fan failure triggering chain reactions. After all, BMW repairs don't come cheap.