What Causes a Burnt Smell from the Car Air Conditioner?
2 Answers
Car air conditioner emitting a burnt smell may be due to mold growth on the surface of the heat exchanger fins, producing a musty odor (similar to traditional Chinese medicine or a scorched smell). The musty smell occurs because moisture and mold accumulate on the indoor heat exchanger of the air conditioner and cannot completely evaporate, forming mold spots. Over time, this results in a musty odor when the AC is turned on. Generally, the mold growth process happens during the cooling cycle, but the smell can become more pronounced during heating. It could also be a burnt smell from some plastic components heating up, which is more common in new cars. If there is a strong burnt smell or an electrical burning odor, it is advisable to stop using the air conditioner immediately and have it checked at a repair shop promptly.
Last time I drove my friend's old car, there was a burnt smell as soon as the AC was turned on. After checking, it turned out the fan motor bearing was stuck without lubrication, overheated, and burned the lubricating oil. This situation is quite common, especially in older cars where the blower motor ages, the rotation speed isn't sufficient, cooling is poor, and the motor coil heats up due to friction. If the compressor lacks refrigerant and the pressure is too high, it can also overheat, burn through the pipes, or cause a short circuit melting the plastic casing. I suggest stopping the car immediately, turning off the engine, and checking the source of the smell to see if it's in the engine area. A simple self-check involves pulling out the fuse to see if it's melted. Delaying repairs might lead to an electrical fire, resulting in the entire car being totaled at a much higher cost. Annual AC maintenance, cleaning the condenser, and replacing the filter can prevent such issues, saving money and ensuring safety. If you encounter a burnt smell, don't keep driving—ventilate to cool it down and then tow it to a repair shop for a full system pressure and voltage test to prevent small issues from becoming major disasters. I often hear people say that repairing a burnt motor is tough, and I've personally seen wires melt and smoke, which is extremely dangerous—it's better to address it early to ensure safety.
