Why does the car's air conditioning have no wind in gears 1-3 but has wind in gear 4?
3 Answers
The reason why the car's heater switch only has wind in the fourth gear is due to the burnout of the heater speed control resistor. Below is a related introduction to the car air conditioning system: 1. Introduction to car air conditioning: The car air conditioning system consists of a compressor, condenser, throttle element, evaporator, fan, and necessary control components. It is used to regulate the temperature and humidity inside the car, providing a comfortable environment for the driver. 2. Working principle: When the compressor is working, it sucks in low-temperature and low-pressure gaseous refrigerant from the evaporator. After compression, the temperature and pressure of the refrigerant increase, and it is sent to the condenser. Inside the condenser, the high-temperature and high-pressure gaseous refrigerant transfers heat to the outside air passing through the condenser and liquefies, turning into a liquid. When the liquid refrigerant flows through the throttle device, its temperature and pressure decrease, and it enters the evaporator. Inside the evaporator, the low-temperature and low-pressure liquid refrigerant absorbs heat from the air passing through the evaporator and evaporates, turning into a gas. The gas is then sucked into the compressor again for the next cycle.
I recently dealt with a similar issue where the AC had no airflow on settings 1-3 but worked fine on 4. It's most likely a faulty blower motor resistor. That part sits near the blower motor and controls the current for lower speed settings. Reach behind the glove compartment and you'll find a matchbox-sized component with wires. If it feels hot to the touch or smells burnt, that confirms it. I'd suggest replacing the resistor first—it costs around 100 yuan and isn't labor-intensive. If that doesn't fix it, check for corrosion on the blower switch connectors or listen for unusual noises from the blower motor itself. By the way, don't keep running it on setting 4—it's noisy and drains the battery. Just take it to a repair shop for proper diagnosis.
I've seen this kind of failure a lot in older cars, especially models like the Sagitar and old Polo. The core reason is the failure of the blower speed control module. When it operates at low speeds, it reduces voltage through resistors. If the resistor breaks, the 1-3 speeds stop working. Another less common reason could be poor contact inside the air conditioning control panel, especially in older cars where button wear can easily cause signal interruptions. It's recommended to first listen for a clicking sound in the glove compartment when switching to speeds 1-3. If there's no sound, it's 90% likely a resistor issue. Additionally, check the condition of the cabin air filter. If it's completely clogged, the weak airflow at low speeds can easily be mistaken for no air. Cleaning the air ducts while you're at it is also a safer bet.
