What is the reason why the car air conditioner only has wind at the 4th speed?

[SanSienna]

The reason why the car heater switch only has wind at the fourth speed is due to the burnout of the heater blower speed control resistor. Specific information is as follows: 1. The solution is to promptly go to the car's 4S shop or repair shop to replace the heater blower speed control resistor, which can solve the problem of the car heater's air outlet failure. 2. Automatic air conditioning and manual air conditioning: Both automatic and manual car air conditioners are similar when turning on the heater. They both adjust the temperature by rotating the temperature control button, with the red area indicating an increase in temperature. However, the automatic air conditioner can set a specific temperature, and it will automatically adjust based on the temperature inside the car. Some car owners, afraid of the cold, turn on the heater immediately after starting the vehicle, thinking it will quickly raise the interior temperature, but this method is actually not effective.

[DeAlaina]

My car had the same issue last time, where only the 4th speed of the AC worked, and the other speeds had no airflow. This problem is mainly caused by a faulty blower motor resistor, which is responsible for adjusting the fan speed at other levels. If it's damaged, the current won't flow properly at low and medium speeds, leaving only the highest speed with direct power. When I checked, I found all the fuses were fine, and replacing the resistor fixed the issue. Additionally, aging switch contacts can also cause this problem—poor contact may lead to the failure of other speed settings. I recommend first checking the fuse box under the dashboard to see if the AC-related fuse is blown. If it's fine, have a technician replace the resistor—it's inexpensive and quick. Avoid always using the highest fan speed, as it can easily burn out the resistor and affect cooling performance. Get it fixed early to avoid discomfort from heat in summer or cold in winter.

[MacBrandon]

I've encountered the issue where the AC only blows air at the 4th speed setting, which can be quite annoying. When set to lower speeds, the airflow either weakens or stops working entirely. The main culprit is often a faulty blower motor resistor module. This resistor regulates low and medium fan speeds - when it fails, you're left with only full-speed airflow. Wiring shorts or breaks could also cause speed control failure. My suggestion is to first check the fuse yourself (usually in the driver-side fuse box, replace the marked one if needed). If that doesn't work, it might be a blower motor issue or switch internal wear. For daily driving, avoid prolonged high-speed usage to extend component lifespan. Leaving it unrepaired makes temperature control difficult, especially uncomfortable during long trips - better get it checked at a shop promptly for safety.

[Harriet]

No air from car AC at low speeds? I tried fixing it. A faulty blower motor resistor is a common cause—it controls speeds 1-3, and when broken, current only reaches speed 4. The resistor module is prone to aging or short circuits. Checking is simple: first inspect the fuse in the fuse box for burns, replace it to test; if that doesn’t help, the resistor might be the issue. Buying a resistor online and replacing it isn’t complicated and is low-cost. Other causes like loose wiring or poor switch contact can be checked with a multimeter. Don’t delay, as cabin heat can affect driving. Act fast or consult a professional.