What is the reason for one car radiator fan spinning while the other does not?
3 Answers
1. Inaccurate water temperature: Most modern car radiator fans operate electronically based on temperature control. Therefore, the fan typically starts spinning normally only when the car's internal water temperature reaches the required level. If the temperature is too low, the radiator fan will not spin. Hence, if the car radiator fan fails to spin, the first thing to check is whether the water temperature meets the requirement. 2. Relay malfunction: If the water temperature is appropriate but the car radiator fan still does not work, the issue might lie with the fan's relay. A faulty relay can prevent the car radiator fan from operating. 3. Temperature control switch problem: If the above two aspects are not the issue, then the temperature control switch should be inspected. This component can sometimes develop faults, which may affect the operation of the car radiator fan, so it should also be checked carefully.
In such cases, it's usually a problem with the fan motor itself. The most common issue is that the non-rotating fan motor is burned out or seized. Under prolonged high-temperature operation, the carbon brushes are prone to wear, and the bearings may also lack lubrication and get stuck. Another possibility is poor electrical contact, where loose or oxidized connectors prevent current from passing through. Relay failures are also common, especially with independent relays controlling different fans—if one fails, the corresponding fan will stop working. Additionally, a malfunctioning temperature control switch or sensor may fail to send the start signal on time. During regular car washes, avoid directing high-pressure water jets straight at the motor. During maintenance, ask the technician to check if the fan connectors are secure.
Last time the fan on the passenger side of my car suddenly stopped working, so I specifically went to an auto repair shop to have it checked. The mechanic found that the motor was broken. The technician said that when the fan stops working, first rule out simple issues: check if the corresponding fuse for the fan in the fuse box has blown, then inspect whether the relay is functioning properly. If the motor is powered but stuck, it's mostly due to rusted bearings or debris blocking the blades. Aging and damaged wiring are also common issues; a loose connection can cut off power. In summer when the AC is on, both fans should be running simultaneously. If only one is working, it's crucial to get it fixed promptly, otherwise the cooling efficiency won't keep up and the engine can easily overheat. It's recommended to visit a professional shop to measure the motor's resistance value to determine its condition.
