Reasons Why the Car Electric Fan Doesn't Spin at Low Speed but Works at High Speed
4 Answers
If the thermostat fails to open, it indicates a damaged thermostat. If the fan doesn't spin at low speed, it could be due to a faulty fan relay or, in some vehicles, a damaged temperature control switch. If neither of these is the issue, then the electric fan itself is likely damaged. Below is relevant information: 1. Thermostat: A thermostat is a valve that controls the flow path of coolant. It is an automatic temperature-regulating device, typically containing a temperature-sensing component that opens or closes the flow of air, gas, or liquid through thermal expansion or contraction. 2. Fan Relay: A relay is an automatic switching component with isolation functionality, widely used in remote control, telemetry, communication, automatic control, mechatronics, and power electronic equipment, making it one of the most crucial control components.
Last time the electric fan in my car malfunctioned - it wouldn't spin at all at low speeds but worked normally at high speeds, which gave me a real headache. Later I discovered several possible causes: First, the fan control unit might be defective, like a relay getting stuck or worn out in low-speed mode; Second, a faulty temperature sensor misreading engine conditions and only sending high-speed signals; Third, poor wiring connections or aging components, such as a burnt resistor blocking current flow at low speeds; Fourth, issues with the fan motor itself, like dry bearings preventing startup at low speeds. This is no minor problem since fan operation directly affects engine cooling - while high-speed operation might barely suffice, insufficient cooling at low speeds increases the risk of overheating. I recommend checking fuses and connector plugs immediately, and if that doesn't help, take it to a professional shop for circuit testing.
Having repaired numerous vehicles, I've found that issues with the electronic fan not working at low speeds but functioning at high speeds often stem from the control components. For instance, the fan relay may have oxidized contacts in low-speed mode, leading to poor conductivity and insufficient current flow. A burnt resistor inside the control module can also cause the low-speed setting to become unresponsive. Additionally, if the sensor signal is incorrect, the ECU may mistakenly activate the fan only at high speeds. Aging wiring and unstable voltage can similarly trigger such symptoms, especially in humid environments where corrosion at wiring connections is more common. When encountering this issue, first use a multimeter to measure voltage at key points, such as checking whether the control module receives a low-speed signal input. Simple cleaning of connectors and fuses can often resolve the problem. For prevention, don't overlook regular maintenance of the fan system, as relying solely on high-speed operation may temporarily suffice but will ultimately increase engine strain over time.
I've been working with cars for decades, and look how complicated these modern electric fans are! The old mechanical fans never had these issues! The common problem of not spinning at low speeds but working at high speeds is usually due to aging electronic components—maybe loose or worn parts in the fan control box that can't generate enough power at low speeds. Reduced sensor sensitivity might also only wake the fan under extreme heat. Oxidized and brittle circuit connections are another big deal, as they can fail to send low-speed signals under insufficient voltage. Back in the day, if my old car's fan stopped working, I'd just test it manually. Nowadays, I'd advise younger folks to first check the fuse box and replace any blown fuses. If that doesn't work, they'll need professional tools for diagnostics. Maintenance-wise, avoiding overheating is crucial—otherwise, fan issues can easily escalate into major repairs.
