What is the reason for the car air conditioning blower only working in the first gear but not in other gears?
3 Answers
The reasons for the car air conditioning blower only working in the first gear but not in other gears are as follows: Poor contact: The main control switch has poor contact, and the switch should be replaced in time. Use a multimeter to measure the contact resistance of the main control switch, and the main control switch or the fan motor coil should be replaced promptly. Wire port damage: Damage to the fan motor wire port. Loose screws: The fastening screws between the fan motor and the fan blade are loose, and the fastening screws should be tightened. Fan capacitor open or short circuit: The fan capacitor is open or short-circuited. The capacitor should be checked promptly, and if necessary, a capacitor of the same specification should be replaced in time.
A few days ago, my relative's car had the same issue—the AC blower only worked on the lowest setting. The experienced mechanic said it's a classic case of a faulty speed control resistor because the first setting bypasses the resistor module and works directly. The other settings require the resistor to control the speed, and the nichrome wires inside the module are very thin, making them prone to melting during continuous summer use. You’ll need to remove the small silver box behind the glove compartment on the passenger side—it contains four or five sets of resistor wires, and you’ll likely find the burnt one. If the resistor isn’t burnt, check if the contacts for settings 2/3/4 on the blower switch are oxidized—a common issue in older cars. A loose wiring connector could also prevent the signal from being transmitted.
My old car had the same issue last summer, where only the lowest fan speed worked. I specifically researched the principle: the blower's multiple speed settings rely on a resistor for voltage reduction and speed control. The first speed is a direct circuit, so as long as the motor isn't broken, it can run. Higher speeds require the resistor module to intervene, which is particularly fragile under high temperatures. During the repair, it was found that the resistor assembly's pins were burnt out. When replacing the new part, remember to apply some conductive paste on the metal pieces to prevent oxidation. I also had the mechanic check if the fan impeller was jammed with leaves, as lack of bearing lubrication can indirectly cause resistor overload. Now, after the repair, I clean the air conditioning filter before every rainy season to prevent the blower from overworking.
