Will the Fan Rotate When the Car's Air Conditioning is Off?
3 Answers
When the air conditioning is off, the fan will still rotate once the coolant reaches a certain temperature. Axial Fan: The blades of an axial fan push air to flow in the same direction as the shaft. The impeller of an axial fan is somewhat similar to a propeller. During operation, the majority of the airflow moves parallel to the axis, meaning it flows along the axial direction. The power consumption of an axial fan is lowest when the inlet airflow is free air with zero static pressure. As the back pressure of the airflow increases during operation, the power consumption also rises. Centrifugal Fan: When a centrifugal fan operates, its blades push air to flow in a direction perpendicular to the shaft (i.e., radial direction). The intake is along the axial direction, while the exhaust is perpendicular to the axis. In most cases, an axial fan is sufficient to achieve the desired cooling effect. However, if the airflow needs to be rotated 90 degrees for exhaust or higher air pressure is required, a centrifugal fan must be used. Strictly speaking, blowers also fall under the category of centrifugal fans.
I've been driving small cars for many years, and the fan will still run even without turning on the air conditioning, mainly to cool the engine. Once the temperature sensor detects that the engine is hot, the fan will start, regardless of whether the air conditioning is on or not. Like last time during a long-distance trip when stuck in traffic, the fan was buzzing loudly. I worried it might be a malfunction and pulled over to check, only to find it was just normal cooling. If the fan doesn't run, it could be due to a blown fuse or a faulty relay, which can cause the engine to overheat and get damaged—that would cost a lot to repair. It's actually a good thing if the fan keeps running for a while after parking to dissipate residual heat, as it shows the system is working. Make it a habit to pay attention to the fan's sound and address any issues early, so you don't end up stranded on the road.
The car fan usually runs even when the air conditioning is off because its primary task is not for the AC, but to cool down the engine. The fan activates when the engine temperature rises, controlled by the ECU, to prevent overheating and engine seizure. If the fan doesn't spin, common causes include a blown fuse, a faulty relay, or dust accumulation jamming the blades. From my experience, listening to the fan noise after climbing a slope can help determine if the cooling system is functioning properly. Low coolant levels in the cooling system may also cause the fan to stop working, so it's essential to regularly check fluid levels and ensure components are unobstructed. Proper daily maintenance of the vehicle ensures a longer fan lifespan—don't skimp on small expenses to avoid major issues.
