How To Operate A Fan Without A PWM Speed Control Line

If the PWM speed control line is not connected, the fan can still operate, but it will run at its default speed.
When it comes to the circuit connection of the fan, there are several key wires that need to be connected: the power cord, ground wire, and PWM speed control wire. The power cord and ground wire respectively provide power and ground connection, while the PWM speed control line is a control signal that can control the speed of the fan by changing the duty cycle of the signal.
For fans with only power and ground wires, they can only operate at the default speed and cannot be adjusted at any speed. This is because this type of fan is usually designed for a single speed and cannot be adjusted through PWM speed control lines.
On the other hand, if the fan has three or more wires, one of which is a PWM speed control wire, it can control the fan speed by turning on or off the PWM speed control wire. If the PWM speed control line is connected to an appropriate circuit, the fan can be adjusted for speed, but if the PWM speed control line is not connected, the fan will operate at the default speed.
In addition to the issue of default speed, not connecting the PWM speed control line may also cause other problems. If you improperly or completely disconnect the PWM speed control line, the fan may emit abnormal noise or vibration, and may overheat or operate abnormally.
This is because the PWM speed control line is not only a wire that controls the fan speed, but also can transmit information about the operating status of the fan, such as speed, power, temperature, etc. If you do not connect the PWM speed control line, you will not be able to obtain this information, which may lead to unpredictable operating behavior of the fan.
Moreover, if you need to control the speed of the fan, you must correctly connect the PWM speed control line. It should be noted that if you are connecting a fan with PWM speed regulation function, but your motherboard or fan controller does not support PWM speed regulation, then even if a PWM speed regulation cable is connected, the fan will not be able to adjust speed. In this case, the fan may run but can only run at the default speed. If you are unsure how to properly connect the PWM speed control cable, it is best to check the fan's user manual or contact the manufacturer to ensure that all necessary wires are correctly connected.
Summary: Fans without PWM speed control cables can operate, but will not be able to perform any speed control. To control the speed of the fan, it is necessary to correctly connect the PWM speed control line and ensure that the motherboard or fan controller supports the PWM speed control function.