What is the reason for the car's cooling fan running constantly when the water temperature is not high?
4 Answers
The reasons for the car's cooling fan running constantly when the water temperature is not high are: 1. Failure of the cooling fan assembly or its wiring; 2. Detachment of the engine water pump impeller or damage to the water pump; 3. Malfunction of the water temperature sensor. The solutions for this issue are: 1. Inspect the fan wiring; 2. Replace the water pump and water temperature sensor. The reasons for an increase in car water temperature include: 1. Leakage in the cooling system or insufficient coolant; 2. Malfunction of the water temperature gauge; 3. Excessive scale in the cooling system, leading to poor heat dissipation; 4. Loose or broken water pump or fan belt; 5. Engine operating under prolonged overload conditions.
My car also had the issue of the fan running continuously even when the engine temperature wasn't high. As someone who's been driving for over twenty years, I've found several possible main causes: a faulty sensor, such as the coolant temperature sensor sending false high-temperature signals; a malfunctioning fan control module or relay, where stuck contacts cause continuous power supply; short circuits or poor connections due to aging wires or rodent damage; and the air conditioning system forcing the fan to run for cooling, which shouldn't happen when the coolant temperature is normal. I once fixed it myself by replacing a faulty relay, which solved the problem. I recommend first checking the fan control box and fuses. If you can't resolve it, take it to a professional repair shop. Don't ignore this seemingly minor issue, as a continuously running fan can drain the battery, leaving you unable to start the car after parking. Also, inspect the wiring during regular car washes to reduce unexpected issues.
From my perspective as a DIY car repair enthusiast, there are several common reasons why the cooling fan keeps running even when the engine temperature isn't high: First, it could be a faulty temperature sensor giving false readings, making it think the engine is overheating. Second, the fan relay might be stuck with its contacts failing to open properly. Additionally, a short circuit in the wiring could cause direct current flow to the fan. Also, the air conditioning system may force the fan to run when in operation. I've personally tested the sensor output with a multimeter - if the signal is abnormal, simply replace it. The checking method is straightforward: unplug the fan connector to see if it still receives power, or test the relay contact resistance. If you have some electrical knowledge, replacing components yourself can save money; but avoid tampering with high-voltage parts as it may damage electrical components. While this seems like a minor issue, neglecting it can lead to premature fan failure and reduced cooling efficiency.
As a safety-first driver, I would say the biggest danger of the fan running constantly when the water temperature isn't high is that it drains the battery, potentially leaving you unable to start the car after shutting it off. Causes include sensor failure, control circuit errors, or relay issues. Don't delay if you notice this - immediately pull over to check the fan fuse or try a simple system reboot. If that doesn't work, stop driving and contact a mechanic, as unexplained fan operation may indicate other underlying issues. Regular maintenance checks of the cooling system can help prevent this situation.
