Why is the car air conditioner not cooling on the driver's side but working normally on the passenger side?

[LeAllison]

Issues with the air duct switch, blocked air ducts, or dirty air conditioning pipelines. Below are more related details: Issues with the air duct switch: If the driver's side is not cooling but the passenger side is normal, it indicates that cold air is not circulating properly. Try switching between the internal and external air circulation modes a few times. When using the air conditioner, avoid keeping the external circulation mode on continuously. Running the air conditioner while the external circulation is on will draw hot air from outside into the car, reducing the cooling efficiency. Therefore, in hot weather, switch back to internal circulation as soon as possible after ventilating with external circulation. Blocked air ducts or dirty air conditioning pipelines: Turn the fan to its maximum setting and check the airflow at the vents with your hand. If the airflow is noticeably weaker than before, it is likely that the air ducts are blocked. The car's air conditioning system includes an air filter, usually located behind the glove compartment on the passenger side (though there are exceptions, such as above the accelerator and brake pedals).

[MacBrianna]

I've encountered this situation a few times in over twenty years of driving. When the air conditioning on the driver's side doesn't blow cold air while the passenger side works normally, it's mostly an issue with the dual-zone climate control system. Take my old Accord for example - the problem was caused by a faulty blend door actuator on the driver's side, which got stuck in the heating position. This component controls the mix of hot and cold air, and when it fails, temperature adjustment becomes impossible. Other potential causes include a faulty blower motor resistor or climate control module malfunction, which can also lead to single-side failure. During my last visit to the repair shop, I learned that evaporator icing typically affects the side closer to the evaporator first. I'd recommend first checking if the climate control settings accidentally have different temperatures set for each zone, then inspecting the actuators and control modules. The repair isn't expensive - replacing a small motor usually costs just a few hundred yuan.

[McRobert]

As an experienced air conditioning repair technician, when encountering a situation where the driver's side is not cooling while the passenger side is functioning normally, we typically first rule out three possibilities: First, a malfunction in the driver's side air blend door actuator, preventing cold air from passing through; second, a blower motor resistor issue, causing insufficient airflow on the driver's side, making it feel like there's no cooling; third, insufficient refrigerant or a leak. When refrigerant is low, the system prioritizes cooling the main circulation loop, and in many car models, the passenger side evaporator happens to be in this prioritized position. Another possibility is slight frost formation on the evaporator, where the driver's side is more prone to icing and blockage. During repairs, it's necessary to connect a diagnostic computer to read the air blend door angle data and use an endoscope to check if the door is stuck.

[DeJulian]

A few days ago, my Sagitar had this issue: the passenger side was freezing cold while the driver side was blowing hot air. After inspection, it turned out to be a problem with the dual-zone climate control system—the driver-side blend door actuator was stuck due to debris. In such compact cars, each seat has independent temperature control flaps. If the driver-side flap gets stuck in the heating position, it completely stops cooling. Resetting the system at the dealership didn’t help, and the issue was only resolved after dismantling the dashboard to clean the track. The mechanic advised regular replacement of the cabin air filter to prevent dust buildup, which can easily jam the flaps. Additionally, the passenger-side evaporator is closer to the AC compressor, so when refrigerant is low, that side may actually feel cooler.