Why is there no air in the 1-3 gears of the car air conditioner but air in the 4th gear?
2 Answers
If there is no air in the 1-3 gears of the car air conditioner but air in the 4th gear, it could be due to a faulty blower resistor. Below is an introduction to car air conditioners: 1. Air Conditioner Layout: Different types of air conditioning systems have different layout methods. Currently, most cars use an integrated heating and cooling air conditioning system. The layout involves assembling components such as the evaporator, heater core, centrifugal blower, and control mechanisms together, known as the air conditioner assembly. 2. Air Conditioner Components: Modern air conditioning systems consist of a refrigeration system, heating system, ventilation and air purification devices, and a control system. A car air conditioner generally includes components such as the compressor, electronically controlled clutch, condenser, evaporator, expansion valve, receiver-drier, piping, condenser fan, vacuum solenoid valve, idle speed controller, and control system. The car air conditioner is divided into high-pressure and low-pressure lines. The high-pressure side includes the compressor output side, high-pressure lines, condenser, receiver-drier, and liquid lines; the low-pressure side includes the evaporator, accumulator, return lines, compressor input side, and compressor oil sump.
I encountered a similar situation during a road trip last summer. I was driving an older family car when suddenly the first three AC speed settings stopped blowing air - only the fan noise remained. Only the highest setting could produce cold air, which left me sweltering. Later at the repair shop, I learned this was likely caused by a faulty blower motor resistor. That small component regulates airflow at lower speeds; if it burns out or has poor contact, the lower settings won't receive power, leaving only the fourth speed (which directly connects to high-speed mode) operational. Additionally, internal switch wear or dust accumulation can cause similar symptoms. Don't delay - get it checked promptly, as prolonged use of the highest setting may overheat the motor or even affect battery life. It's best to have a professional mechanic test the circuit with a multimeter. During regular maintenance, clean dust around the fan area to prevent blockages and avoid minor malfunctions. If this happens while driving, stay calm - first open windows for ventilation to ensure safety.
