Why does the fan not rotate at the first speed but starts rotating at the third speed?
4 Answers
When the fan does not rotate at the first speed but starts rotating at the third speed, it is due to a decrease in the capacitance of the fan's starting capacitor. Replacing it with a capacitor of the same capacity can solve the issue. Below is an introduction to related content: 1. Classification: Fan capacitors are generally divided into two types: starting capacitors and running capacitors, which function based on their roles during operation. 2. Starting capacitor: The starting capacitor assists the motor during startup and becomes inactive once the motor is running; the running capacitor continues to assist the motor even after startup, meaning it remains active. The capacitor in an electric fan is usually a starting capacitor.
Recently, my own car also encountered the strange issue where the fan's first speed stopped working and only the third speed functioned. It’s probably due to the aging of the fan resistor. That component is located behind the blower and specifically controls the speed of different fan settings. If the resistance wire for the first or second speed burns out or has poor contact, those speeds will fail, causing the fan to jump directly to higher speeds. Loose wiring connections could also be the culprit, especially in older cars where plugs are prone to oxidation and corrosion. Unstable voltage in the air conditioning system can also cause erratic fan speed changes and, over time, shorten the motor's lifespan. I recommend first checking the fuse box on the dashboard to see if the fuse corresponding to the fan has blown—replacing it costs just a few dozen yuan. If that doesn’t solve the issue, it’s best to visit a repair shop and use a multimeter to test the resistor value, avoiding the discomfort of a malfunctioning AC during summer traffic jams.
As someone who enjoys DIY, when I notice the fan doesn't work on the first speed but spins on the third, I immediately check the resistor module. It's installed near the fan to control the airflow. The resistor components used for low speeds may overheat, potentially causing a fuse to blow or corrosion, leading to speed skipping. Loose or worn wiring contacts can also cause this issue. Additionally, inspect the fan switch contacts for aging, as frequent adjustments can accumulate dust and looseness. Remember to test the switch feedback first—if the clicking sound is still normal, the problem likely lies in the resistor section. If you're doing it yourself, don't cut corners; wear protective gloves when checking wiring connections to ensure no risk of short circuits. These minor faults aren't major trouble, but neglecting them could affect the entire AC system's efficiency. Fixing them usually just requires spending a little to replace components.
Why does the fan stall in low speed but work in high speed? Most likely the resistor is faulty—it limits current to reduce airflow in low settings, but when damaged, current bypasses it and directly powers the motor, making the fan spin at high speed. Wiring degradation can also break connections, especially in the hot engine bay where plastic insulation cracks easily. Loose switch contacts are another common culprit; flicking the switch repeatedly may reveal weak clicking sounds. Check fuses and wiring harness connections promptly to avoid turning your car into a sauna in hot weather.
