After a cooling fan has been in use for some time, the core reasons for the increased noise are mechanical wear, foreign object accumulation, structural deformation, or lubrication failure.

These reasons can be broken down into the following specific categories, and understanding the underlying principles and manifestations will make it easier to identify the exact cause:

一、Core Cause: Wear and Aging of Mechanical Components

The "quiet operation" of a fan relies on the precise coordination of components such as bearings and fan blades. Over long-term use, the coordination gaps widen and components wear out, directly leading to noise. This is the most common root cause.

1、Bearing Wear (Highest Proportion)

The core rotating component of a fan is its bearing, which is mainly divided into oil-impregnated bearings and ball bearings. The manifestations of wear differ slightly between the two:

Oil-impregnated bearings: Inside these bearings, a lubricating oil film forms to reduce friction. After long-term use, the lubricating oil may evaporate, dry out due to high temperatures, or become ineffective due to dust contamination. This causes direct metal-to-metal friction in the bearings, producing a continuous "hum" noise. The higher the rotation speed, the more obvious the noise, and slight vibration may even occur.

Ball bearings: These bearings contain steel balls and a cage. After prolonged use, wear marks will appear on the surface of the steel balls, and the cage may deform or loosen. This leads to "jamming" or "impact" when the steel balls roll, resulting in noises such as a "rustling" friction sound or intermittent "clicking" sounds. Moreover, the noise will gradually worsen after wear occurs and cannot be resolved through simple lubrication.

2、Aging and Deformation of Fan Blades

Most fan blades are made of plastic. When exposed to high-temperature environments for a long time (e.g., near CPUs or power supplies), they undergo thermal aging:

The edges of the fan blades may become slightly deformed. When rotating, they can no longer maintain uniform air flow, generating "turbulent noise" (similar to messy "whooshing" wind sounds).

The center of gravity of the fan blades may shift (e.g., uneven thickness due to local aging). This causes "dynamic imbalance" during rotation, leading to overall vibration of the fan. The noise is accompanied by a noticeable "shaking sensation", and in severe cases, the blades may collide with the fan frame, producing a "tapping" sound.

二、Common Trigger: Foreign Object Accumulation and Contamination

Foreign objects such as dust and hair disrupt the normal operating environment of the fan. They not only increase resistance but also accelerate wear, acting as "accelerators" for increased noise.

1、Bearing/Fan Blade Blockage by Dust

Dust in the air enters the bearing interior as the fan rotates and mixes with lubricating oil to form "oil sludge". This not only hinders lubrication but also increases the frictional resistance of the bearings, causing the noise to change from "quiet" to a "muffled hum". At the same time, dust accumulated on the surface of the fan blades alters the aerodynamic structure of the blades. When rotating, air disturbance increases, resulting in "noisy wind".

2、Entanglement by Hair/Fibers

If the fan is used in an environment with a lot of hair (e.g., desktop fans or chassis fans near the ground or pet activity areas), hair will wrap around the "root of the rotating shaft" or the "edges of the fan blades". On one hand, this obstructs the rotation of the shaft, increasing the motor load and raising noise levels. On the other hand, the entangled hair causes the fan blades to "scrape" against the fan frame during rotation, producing a "squeaking" scraping sound.

三、Other Secondary Causes: Installation or Environmental Factors

These causes are not faults of the fan itself, but they can amplify existing noise or generate new abnormal sounds, which are easily mistaken for fan aging.

1、Loose Installation or Resonance

If the screws are not tightened properly during fan installation (e.g., chassis fans or heatsink fans), the main body of the fan will shake slightly when rotating, creating "resonance noise" with the chassis/heatsink. This manifests as a "low-frequency hum", and the noise will significantly decrease when you press the fan with your hand.

If the fan is incompatible with the installation position (e.g., excessive gap between the fan size and the bracket), the edges of the fan blades will collide with the bracket intermittently during rotation, producing a "tapping" impact sound.

2、Unstable Voltage/Current

The rotation speed of some fans (e.g., CPU cooling fans) depends on voltage regulation. If the output voltage of the power supply fluctuates or the motherboard’s temperature control circuit malfunctions, the fan speed will "speed up and slow down alternately", and the noise will change accordingly (e.g., "loud for a while, quiet for a while"). In extreme cases, excessively high voltage will cause the fan to operate beyond its load, generating a sharp "high-frequency noise".

3、Excessively High Ambient Temperature

When the internal temperature of a device (e.g., a computer or projector) is too high, the fan will automatically increase its rotation speed to enhance heat dissipation. The higher rotation speed directly leads to louder "wind noise". This is a normal protective mechanism of the fan; the essence is an "increase in heat dissipation demand" rather than a fan fault. The noise will subside once the temperature drops.

四、Summary: Quick Methods to Identify the Source of Noise

1、Rotate the fan blades by hand after powering off: If rotation is stuck or you feel friction, it is most likely due to bearing wear/oil sludge blockage. If rotation is smooth but the fan blades shake noticeably, the issue is fan blade deformation or dynamic imbalance.

2、Inspect the fan blades and bearings: If there is obvious dust or hair on the surface, the problem is foreign object accumulation. If there is no lubricating oil at the bearing (dry and shiny), it indicates lubrication failure.

3、Press the fan while it is running: If the noise decreases after pressing, the cause is loose installation or resonance. If there is no change after pressing, the issue lies in internal component wear.

For different causes, solutions such as "cleaning dust, adding lubricating oil, or replacing bearings/fan blades" can be adopted. If wear is severe (e.g., broken steel balls in the bearing or fractured fan blades), it is recommended to replace the fan directly to avoid heat dissipation failure caused by the fault.

Capital Technology Co., Limited is the chief agent of SANYO DENKI, one of the leading enterprises of the cooling fan industry. We are a factory who also have our own independent brand CAPITAL product series. The main products are cooling fan, DC/AC fan, radiator, filter, reactor etc. We can provide customer with the most professional and perfect technical support, welcome to contact me at anytime at rainlee@szcpt.com.