What are the reasons for the car engine fan not spinning?

[SanCali]

Engine fan failure to rotate may be due to a blown fuse or a faulty thermal switch. The cooling fan in the engine compartment operates under two conditions: when the engine coolant is at a high temperature and when the air conditioning is turned on. If the fuse is blown, do not replace it with copper or iron wires as a substitute under any circumstances to avoid causing greater damage. It is advisable to promptly visit a repair shop for professional service. If the issue is not a blown fuse, then check whether the fault is caused by a damaged cooling thermal switch. The inspection method is as follows: without starting the engine, turn on the ignition switch and activate the A/C switch of the air conditioning. If the electric fan spins, it indicates the thermal switch is damaged. If the electric fan does not spin, it is highly likely that the electric fan itself is faulty. In case of a damaged thermal switch, you can unplug the thermal switch connector, prepare a roughly 10 cm long insulated wire, strip a section of insulation from both ends to expose the copper wire, and connect it to the two terminals of the connector to provide a high-speed circuit for the electric fan. This temporary solution allows you to start the engine and drive to the nearest repair facility. If the electric fan is damaged, the only solution is to replace it to resolve the issue.

[JohnDella]

Last time my car's fan went on strike and really got me worried. Experience tells me to check three areas. For the electrical circuit, first look at the fuse—find the one labeled 'cooling fan' in the engine compartment fuse box, and replace it if it's blown. Then check if the relay makes a clicking sound; if there's no response, it needs to be replaced. Loose or corroded wiring connections are also common culprits. For the mechanical part, the main issues are a seized fan motor or rusted bearings—if turning the blades by hand feels stiff, that's the problem. The trickiest part is the temperature control system: when coolant is low, the sensor won't receive high-temperature signals, and a stuck thermostat can also cause the fan to misjudge the water temperature. I suggest first trying to replace the fuse as a test; if that doesn’t work, head to the shop quickly to check the ECU data stream.

[TimothyMarie]

After repairing cars for over a decade, I've found that if the fan isn't spinning, there's an 80% chance it's an electrical issue. Open the hood and first listen for the relay's operation—you should hear a distinct 'click' during normal startup. If it's silent, unplug the relay and shake it; if there's a rattling sound inside, it's likely toast. The coolant temperature sensor at the bottom left of the radiator is particularly prone to failure—if it malfunctions, the ECU won't receive the high-temperature signal. Also, a damaged radiator fan resistor can cause the fan to get stuck in low speed or stop completely. If you're DIY-ing, check the voltage at the fan connector—it should read 12V with the ignition on. If the connector itself is burnt, the motor windings are probably short-circuited. Don’t forget to regularly clean the radiator to prevent debris buildup, as jammed blades can also burn out the motor.

[McPeter]

Common causes include a faulty temperature switch. This device mounted on the thermostat housing should activate the circuit when coolant exceeds 90°C, but oxidized contacts can prevent proper operation. Insufficient coolant is equally dangerous - low fluid levels leave the sensor dry, falsely indicating low temperature. Fan motor brushes worn to their limit will also cause stoppage, especially in older vehicles over 100,000 km. I've seen seven or eight cases where improperly installed audio system wiring caused circuit overloads that burned out fan fuses. In northern regions, winter road salt corroding wire harness connectors is widespread; using WD-40 on plugs provides temporary relief.

[MacElla]

Fan failure isn't just about cooling issues. Modern vehicles have highly interconnected electronic control systems. For instance, when the AC high-pressure switch fails, the ECU will forcibly stop the fan to protect the compressor. Transmission overheating can also trigger protection protocols. The most bizarre case I've encountered was an alternator output voltage fluctuation - a momentary voltage spike fried the fan control module. Some models require additional checks on the fan viscous clutch to inspect for oil leaks or connection plate failures. For DIY diagnostics, prepare a multimeter to measure voltage: all terminals of fuses/relays should show 12V when powered, and grounding terminal resistance should be below 0.5Ω for normal operation.

[DeColeman]

From a usage perspective, short-distance commuting is the most damaging to the fan. The engine never reaches operating temperature, and condensation water corrodes the motor bearings. If you see radial oil stains on the blade surface, it usually indicates aging of the bearing seal. Another common issue is water ingress into the fan plug causing a short circuit after wading through water during rainy seasons—it might self-recover after drying for two days, but it's best to disassemble and blow-dry it. Cases of overload due to illegally tapping power from the fuse box for aftermarket HID headlights are increasing year by year. A hidden culprit is improper coolant mixture—excessive water content lowers the actual boiling point, and by the time the temperature gauge warns, the fan should have already been running. It's recommended to clean the fan connectors every two years when replacing the coolant.