What is the reason for one car radiator fan spinning while the other does not?

[AnaRose]

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.

[StElias]

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.

[OLola]

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.

[LeLane]

The car cooling system typically operates with dual fans working in coordination. If one fan stops rotating, it can lead to uneven heat dissipation. Possible causes include internal short circuits or open circuits in the faulty fan's motor, or issues with the power supply circuit. For example, burnt relay contacts or blown fuses can interrupt the current. Malfunctions in the fan control module or coolant temperature sensor may also activate only one fan. For the non-rotating fan, check if the motor is overheating due to overload or if the bearings are damaged. Don't overlook the possibility of deformed fan blades—impact during the last car wash could have caused blade deformation and jamming. Immediate action is required upon discovery to prevent overheating of the coolant.

[DeCarmen]

Be alert if one fan stops working when the engine overheats. Common causes include a failed fan relay, burnt motor windings, or oxidized wire connectors causing poor contact. I've encountered cases where vehicle vibration loosened the plug, and simply re-securing it fixed the issue. If the motor is faulty, replacement is needed—but don't rush. First check if the fuse is intact, then inspect the relay. Prolonged fan failure affects radiator cooling efficiency and may lead to cylinder scuffing in severe cases. Recommend checking fan operation during each maintenance service and cleaning the radiator regularly to prevent clogging, which can reduce such problems.

[GriffinAnn]

Having worked in auto repair for over a decade, such failures are common. The main causes include a damaged fan motor, such as worn-out motor brushes or seized bearings. Wiring issues like corroded connectors or short circuits due to damaged wire insulation are also likely. Controller errors can result in signals being sent to only one fan, and faulty temperature control switches can also have an impact. For the fan that isn't turning, first manually rotate the blades to check for movement; resistance indicates a mechanical issue. Then feel if the motor is hot—heat suggests power is reaching it but the motor is faulty. Test fuses using the spare tool substitution method; if that doesn't work, professional circuit testing is needed. Regularly cleaning leaves and debris around the fan after washing the car can reduce the likelihood of seizing.