What methods can be used to increase the rotational speed of a cooling fan when the voltage is insufficient?
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Technology
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Author:
rain
Origin:
capital
Time of issue:
2025-07-23 09:49:59.000
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What methods can be used to increase the rotational speed of a cooling fan when the voltage is insufficient?
When the rotational speed of a cooling fan slows down due to insufficient voltage, measures can be taken to increase the voltage or optimize the fan's operating conditions to restore its speed. Here are specific and feasible solutions, sorted by operational difficulty and applicability:
一、Directly address the issue of insufficient voltage
1、Troubleshoot and repair the power supply line
Check the line connections: Ensure that the fan's power plug, interfaces (such as the motherboard's 4PIN/3PIN interface, power adapter plug) are not loose, oxidized, or have poor contact. Re-plug or clean the interfaces (wipe with a cotton swab dipped in alcohol).
Replace damaged lines: If the internal wires are broken or the outer sheath is aging, directly replace the power cord with the same specifications (pay attention to matching the wire diameter to avoid voltage drop due to overly thin wires).
2、Replace with an appropriate power supply device
Faulty power adapter: If the fan is powered by an external power supply (such as a 12V adapter), use a multimeter to measure the output voltage. If it is lower than the rated value (e.g., nominal 12V but actually only 9V), replace it with an original adapter of the same voltage and current (or higher current). The current must be ≥ the fan's rated current to avoid overload.
Insufficient power supply from the motherboard/power supply: If a computer fan has unstable power supply from the motherboard interface (e.g., multiple devices sharing one power supply line), the fan can be connected to an independent power supply's large 4PIN interface (via an adapter cable) to draw power directly from the power supply, reducing voltage loss.
3、Temporarily increase the voltage (only for low-power fans)
Reverse series connection of diodes (use with caution): If the voltage is slightly low (e.g., a 12V fan actually gets 10V), 1-2 diodes (such as IN4001) can be connected in reverse series in the circuit. Utilize the reverse cut-off characteristic of diodes when forward biased (only applicable to specific circuits; understand the circuit principle to avoid damaging the device).
Use a boost module (recommended): For DC fans (such as 5V/12V), a small boost module (such as XL6009, MT3608) can be connected in series to boost the low voltage (e.g., 8V) to the fan's rated voltage (e.g., 12V). Note that the module's output current must be ≥ the fan's rated current (e.g., if the fan's current is 0.3A, the module must support ≥0.5A), and distinguish between positive and negative poles when wiring.
二、Reduce fan load to indirectly increase effective rotational speed
Even if the voltage is not fully restored, reducing the rotational resistance of the fan can make the actual rotational speed closer to the normal level:
Clean the fan and cooling system: Thoroughly clean dust and hair from the fan blades and bearings (using a soft brush + compressed air), remove stuck debris, and reduce rotational resistance.
Lubricate the bearings: If the fan has high resistance due to dry bearings, add 1-2 drops of special lubricating oil (such as sewing machine oil, fan lubricating oil; avoid edible oil as it easily attracts dust) to the bearings to reduce friction.
Lubricate the bearings: If the fan has high resistance due to dry bearings, add 1-2 drops of special lubricating oil (such as sewing machine oil, fan lubricating oil; avoid edible oil as it easily attracts dust) to the bearings to reduce friction.
Replace with a low-resistance fan: If the original fan's bearings are aging (such as oil-impregnated bearings), directly replace it with a fan of the same specification with ball bearings (which have lower friction resistance and better adaptability to voltage fluctuations).
三、Special treatment for smart speed-regulating fans
If the fan supports PWM speed regulation (such as a computer CPU fan), insufficient voltage may be accompanied by abnormal speed regulation signals:
Check the speed regulation signal: Enter the motherboard BIOS or use software (such as HWMonitor, SpeedFan) to check the fan speed control mode. Confirm if the low rotational speed is due to insufficient voltage in the "voltage speed regulation mode". Switch to "PWM speed regulation mode" (requires support from both the fan and the motherboard), which controls the rotational speed through pulse signals and reduces reliance on voltage.
Turn off intelligent speed reduction: Disable the "low-temperature automatic speed reduction" function in the control software to force the fan to run at maximum speed (only for temporary emergencies, as it may increase noise and power consumption in the long term).
四、Precautions
Safety first: When involving circuit modifications (such as boost modules, line welding), ensure power is disconnected to avoid short circuits. The boosted voltage must not exceed the fan's rated voltage (e.g., a 12V fan should not exceed 13.5V), otherwise, the motor coil may be burned.
Prioritize solving the root cause: Temporarily increasing the voltage is only an emergency measure. It is necessary to investigate the root cause of insufficient voltage (such as power supply failure, line aging) to avoid shortening the fan's service life due to long-term undervoltage or overvoltage operation.
Check compatibility: When replacing the fan or power supply, ensure the specifications match (voltage, interface, size). For example, a 12V fan cannot be directly connected to a 24V power supply, otherwise, it will be burned instantly.
The above methods can effectively solve the problem of reduced fan rotational speed caused by insufficient voltage. Among them, repairing the power supply line and replacing the appropriate power supply are the most fundamental solutions, while cleaning the fan and lubricating the bearings can be used as auxiliary means to improve the fan's operating efficiency under low voltage.
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.
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