Does the Fan Run at Idle Speed?
2 Answers
Generally, the car fan starts running after about 10 minutes at idle speed. Below is an introduction to the fan behavior under idle conditions: 1. The operation of the fan at idle depends on the rate of water temperature rise, which varies from car to car and under different conditions. The time is slightly shorter in summer and longer in winter. When the car is moving, the time is also slightly shorter. 2. Older cars running the air conditioning at idle can be more damaging to the car. In older cars, the engine cooling fan is controlled by the engine crankshaft speed. At idle, the engine speed is low, and the cooling fan speed is also lower. 3. When the engine temperature rises, the water temperature also increases, which can cause some degree of damage to the car engine. 4. For cars produced in the current stage, running the air conditioning at idle does not cause much damage. Modern car engine cooling fans are powered by the battery and automatically adjust their speed based on the engine temperature. If the idle time is long, you can clearly hear the noise from the engine compartment fan becoming louder, which is actually due to the increasing fan speed.
After years of repairing cars, I've found that whether the fan runs at idle depends on temperature. The fan primarily dissipates engine heat and is controlled by electronic systems, such as temperature sensors. Idle means low engine RPM—if the engine isn't hot (like during cold starts or in low-temperature conditions), the fan may not run. However, in traffic jams, with AC on, or during hot weather, the fan often activates at idle to prevent overheating damage. Once, while inspecting a customer's car, the fan wasn't running at idle—turned out to be a faulty temperature sensor, which was replaced to fix it. I recommend regular checks of fan operation; don't wait for major issues to repair.