What Causes Reduced Airflow When Car AC Runs for a Long Time?

[Barbosa]

Reasons for reduced car AC airflow: Blocked dashboard vents; Air leakage in dashboard vent ducts; Abnormal air direction control mechanism; Faulty air direction control motor; Low blower fan speed; Malfunctioning blower speed control module; Frozen AC pipelines; Clogged cabin air filter. Causes of unpleasant odors in car AC systems are as follows: 1. Accumulated dust in interior filters and copper coils: After prolonged use, dust accumulates in the interior filters and copper coils, reaching a certain level that generates odors. When the AC is turned on, these odors disperse into the air. 2. Moisture inside the interior unit: Following cooling/heating operations, moisture often remains inside the interior unit. If the AC lacks a dry anti-mold function and shuts down immediately, this persistent moisture leads to mold growth over time, naturally producing musty odors.

[LaLeila]

I've also experienced reduced airflow after prolonged AC use, which is quite frustrating. The main reasons are: first, a clogged cabin air filter, especially when dust or willow catkins accumulate in the filter—the longer you use it, the more buildup there is, resulting in weaker airflow. Then there's the blower motor overheating; running the AC too long in summer with poor motor cooling causes RPM to drop, naturally reducing airflow. Another common issue is evaporator frosting—excessive cooling causes ice buildup on the evaporator surface, blocking air passages and restricting airflow. Regularly cleaning the filter and letting the motor cool during stops can help, but older models may have faster wear on blower components.

[DaisyAnn]

As someone who drives frequently, I believe there are several common reasons for reduced airflow from the AC. First, the filter may be severely clogged; over time, dust accumulates when the AC is used extensively, obstructing airflow and reducing the wind volume. Second, poor contact or aging of the fan's wiring can cause issues; after prolonged operation, the wires expand and contract with heat, leading to loose connections and reduced airflow. Third, system frosting or blockages can occur; prolonged AC use in high humidity causes condensation that may freeze and block the pipes, thinning the airflow. Sometimes, temperature control settings also play a role; for instance, when the car cools down, the system may automatically reduce airflow to save power. I make it a habit to check the filter every season and keep the fan clean to prevent significant airflow reduction.

[BennettDella]

Hey buddy, if the air flow gets weaker after using the AC for a long time, it's mostly because the filter is dirty. Dust accumulates in the AC system, making it hard to suck air, so the wind gradually weakens. It could also be due to deformed fan blades or the motor overheating, which causes poor heat dissipation and prevents the fan from reaching higher speeds. This issue is more noticeable in older cars that haven't been cleaned. I usually turn off the AC for a break after using it for two or three hours to let the fan rest, or replacing the filter can easily solve the weak air flow problem and even save some fuel consumption.

[ElliotMarie]

I always pay attention to whether the airflow decreases when the air conditioning is on. The first thing I consider is whether the filter is clogged with dust. Running the AC for extended periods can easily lead to dust accumulation, reducing airflow. Secondly, evaporator icing is also quite common. Prolonged cooling can cause moisture to freeze and block the air passages, preventing airflow. Additionally, I check if there's poor contact in the fan circuit, such as a blown fuse or loose wiring, which can easily cause issues affecting airflow during long drives in hot weather. Regular cleaning of the filter and avoiding excessive cooling can prevent problems and ensure smooth air conditioning operation.