What are the reasons for the failure of car air conditioning gears 1, 2, and 3?

[PrestonLynn]

Air conditioning gears 1, 2, and 3 may fail due to a blown air conditioning fuse or a damaged air conditioning circuit board. Below are the specific reasons and solutions: 1. Specific reasons: The air conditioning fuse is blown or the air conditioning circuit board is damaged; the compressor is damaged, or excessive moisture has entered the refrigeration system, reducing the drying effect and causing ice debris to block the pipes. 2. Solutions: If it's a fuse issue, simply go to a repair shop to replace and reinstall it; if there's a circuit problem, it's necessary to check at a 4S shop or a professional automotive electrical repair shop. If it cannot be repaired, it must be replaced.

[BeckettMarie]

Last time my Chevrolet's AC could only operate at the highest setting, the mechanic found a faulty blower motor resistor after inspection. This component controls the medium and low fan speeds and is located behind the glove box. The resistor plates are prone to deformation and failure due to long-term exposure to hot air blown by the fan. Later, it was also discovered that the 20A blower fuse in the fuse box had turned black, and replacing both finally solved the issue. Actually, worn knob contacts can also cause poor connection, especially noticeable in older cars with aged plastic clips. For DIY repairs, it's recommended to first check the fuse location (marked in the vehicle manual), then look for signs of burning on the resistor, and finally test the switch's continuity. If encountering this issue, avoid forcing the AC to run at maximum speed continuously, as it can easily burn out the entire blower motor assembly, leading to higher repair costs.

[McJuliana]

With over a decade of car repair experience, I've found that the most common cause of air conditioning speed control failure is a faulty blower motor resistor. This component is usually located behind the blower fan, where the resistor wire can easily burn out under high temperatures, resulting in no response from speeds 1-3. Secondly, oxidized or worn contacts on the control panel switches can cause similar issues - spraying some contact cleaner when disassembled might provide a temporary fix. Wiring problems are also common, such as loose connectors or rodent-chewed wires. I recommend first checking if the fuse is blown (typically 20-30A), then testing the voltage on the blower motor power wire. When troubleshooting yourself, remember to disconnect the negative battery terminal. The resistor should measure between 0.5-3 ohms on a multimeter to be considered normal. If the resistor is confirmed bad, always replace it with an OEM part - aftermarket parts have inferior heat dissipation and often fail again within three months.

[DelKate]

My old Passat's air conditioner only had four working speeds last year, and it turned out the speed control module was dead. This plastic box is located behind the glove compartment on the passenger side, and you can see it after removing six screws. Inside, two out of the three sets of ceramic resistor plates were burnt and cracked. The auto repair shop said that the low and medium speeds use resistors for current limiting, and prolonged use of speeds one and two can cause heat buildup, making them prone to melting. They recommended using the auto mode more often when running the air conditioner. Another less common reason is worn-out blower motor carbon brushes, which cause unstable current at low speeds. If the first three speeds have no airflow at all but the maximum speed works fine, it's basically one of these two issues. Replacing the resistor myself cost 200 yuan, which is much cheaper than replacing the entire assembly.