What is the reason for the BMW 3 Series fan running non-stop?

[AmeliaLynn]

Fan running non-stop is due to the engine water temperature being too high or even boiling. Here is more information about high engine water temperature: 1. Causes: There are many reasons that can cause the engine water temperature to be too high or even boil, common ones include damage to electronic components in the cooling system (thermostat, cooling fan), poor radiator performance, insufficient coolant, etc. 2. Solutions: Check if the lack of antifreeze is causing the high engine water temperature. Also, check the circulation of the coolant to see if it is not flowing smoothly. Additionally, inspect components such as the water temperature sensor, water pump, thermostat, and cooling fan, as any of these could lead to high water temperature. It is recommended to visit a repair shop for maintenance.

[MacBradley]

This is quite common with the BMW 3 Series, where the fan keeps running continuously, mainly due to minor issues in the cooling system. The usual root cause is a faulty coolant temperature sensor, which detects a high-temperature signal and keeps the fan running, even though the engine temperature is actually normal. It could also be a stuck relay, preventing the fan's power from being cut off. Additionally, insufficient coolant or air bubbles in the system leading to poor heat dissipation can also trigger the fan to run at full power. Long-term operation of the fan can affect battery life, especially consuming power quickly at idle. I recommend first checking if the coolant level is sufficient with a simple visual inspection of the reservoir; if there's no improvement, then it's necessary to use a diagnostic tool to scan for fault codes, as BMW's electronic systems are quite complex. It's best to visit a repair shop promptly to address potential issues.

[VanAlex]

Experiencing a continuously running fan in your BMW can indeed be frustrating, often caused by the temperature sensor misjudging the engine temperature. A constantly operating fan continuously drains the battery, especially in hot weather or during city traffic congestion. Additionally, relay failure is a common culprit, where the fan switch gets stuck and fails to turn off. Insufficient coolant can also prompt the fan to work harder for cooling. If the cooling system itself is clogged, the fan may persist in operation. I once had a similar experience where the fan kept running long after parking, nearly draining the battery and affecting the startup. The solution is to regularly inspect the cooling system, including radiator cleaning and fluid level checks; in severe cases, consult a professional with specialized tools for a thorough diagnosis to prevent potential issues.

[MacEverett]

The BMW 3 Series fan running non-stop is usually not too alarming, with the most likely cause being a faulty temperature sensor causing the system to falsely report high temperatures. The fan running continuously not only creates noise but also consumes electricity, and may even lead to low voltage making it difficult to start the engine. Occasionally, a stuck relay can also cause this, preventing the fan from turning off. Insufficient or deteriorated coolant can also trigger excessive cooling. It's normal for the fan to run briefly after regular driving, but if it runs non-stop for a long time, it's time to pay attention. You can check if the coolant reservoir is full and inspect the fan relay box for any abnormalities. BMWs have high electronic precision, so it's best not to delay and promptly visit a workshop to scan for fault codes for a proper solution.