What is the reason why the BMW 3 Series air conditioner only blows air but does not cool?
4 Answers
BMW 3 Series air conditioner only blows air but does not cool for the following reasons: 1. Lack of refrigerant: Refrigerant wear is mainly due to leakage. If the condenser leaks, the condenser needs to be replaced. When the leakage is severe, oil stains can be seen on the surface of the condenser through the grille, which usually indicates a condenser leakage. 2. Damaged air conditioning flap: Damage to the air conditioning flap motor is relatively rare but not unheard of. The flap motor is usually located in the lower middle part of the instrument panel and serves as the main switch for the air conditioning vents. Once the flap is damaged, even if the air conditioner can cool, cold air can only escape through gaps. 3. Dirty condenser: The purpose of cleaning the radiator and condenser is mainly for heat dissipation. In spring, willow catkins and poplar catkins sticking to the condenser can cause the engine temperature to rise or poor air conditioning performance. When cleaning, be sure to first use an air gun to blow away debris before washing with a water gun, otherwise it may have the opposite effect, leading not only to poor air conditioning but also increased fuel consumption. 4. Damaged air conditioning compressor, throttle valve, or expansion valve: High low pressure and low high pressure indicate the need to replace the compressor. Faults in the expansion valve and throttle valve directly lead to poor air conditioning performance. 5. Aged or loose belt: Generally, during maintenance, the 4S shop will remind you to replace the belt. If it is not replaced, slipping may occur during use, leading to belt breakage, belt noise, loss of power assistance, and poor air conditioning performance.
I've driven several BMW 3 Series, and air conditioning not cooling is quite common. Low refrigerant is likely the main cause, as it naturally decreases over time, and leaks make it even worse. If the AC compressor is damaged, it won't cool either—that thing is the heart of the refrigeration system. Last time, my car's condenser was too dirty, affecting heat dissipation, and the cooling efficiency dropped significantly. Also, check if the expansion valve is clogged—that small part can also cause cooling failure. Another issue is aging and leaking AC lines—the rubber seals become brittle after a few years. I recommend using a diagnostic tool to check the high-pressure side and visually inspect if the condenser is covered with willow catkins. These issues are especially noticeable in summer and should be addressed promptly to avoid affecting engine cooling.
My 3 Series had the same issue where the AC only blew air. The first step is to check the AC button to ensure the cooling mode is activated. Next, verify if the compressor is working by opening the engine compartment and starting the AC—there should be a sound of the electromagnetic clutch engaging. Insufficient refrigerant can cause the system to fail completely; you can check this by feeling the temperature difference between the high and low-pressure lines. The control module might also malfunction, especially if the temperature sensor is faulty, causing the system to misjudge the cabin temperature and not activate cooling. Electrical issues like blown fuses or poor relay contact should also be inspected. I recommend first checking the refrigerant pressure and then systematically ruling out other causes—otherwise, driving in summer becomes unbearable.
Last time my BMW also had the AC blowing air but not cooling, which was unbearable in the hot weather. The mechanic said the refrigerant had completely leaked out, and upon inspection, it was found that the condenser connection was loose. It could also be due to a loose or broken compressor belt, causing the compressor not to run at all. A dirty cabin air filter blocking the air ducts can also affect cooling, but it wouldn’t result in no cooling at all. Another possibility is the evaporator freezing up and blocking the air ducts, though this would reduce airflow. I went straight to the shop for a system diagnosis, and it turned out the control panel switch was faulty—replacing it fixed the issue. If you encounter this in summer, get it checked early; driving without AC is unsafe.
