What is the Principle of High and Low Speed Control for Automotive Cooling Fans?
2 Answers
Automotive cooling fan high and low speed control principle: By installing a relay on the original vehicle voltage to increase the voltage, and then installing a fan resistor to increase a certain resistance value to reduce the current, thereby controlling the motor speed. Below is relevant information: 1. High-speed operation: Generally, radiator fans are electrically driven. High-speed operation of the cooling fan consumes a lot of electricity, which increases the generator's output accordingly and extends the generator's working time. 2. Location: The car fan is installed behind the radiator (on the side close to the engine compartment), and when turned on, it draws air from the front of the radiator; however, some models have fans installed in front of the radiator (outer side), blowing air towards the radiator when turned on. The fan starts and stops automatically based on the coolant temperature. At high speeds, the air pressure difference between the front and rear of the vehicle is sufficient to act as a fan, maintaining the coolant temperature at a certain level.
As an automotive technology enthusiast who has studied numerous repair cases, I find the high and low speed control of car cooling fans quite ingenious. The basic principle involves using a temperature sensor to monitor engine coolant temperature. When the temperature is normal or low, the fan maintains low-speed operation, which is achieved by current limitation through relays, such as adding a resistor to reduce voltage. However, when the coolant temperature becomes too high, the sensor sends a signal, prompting the control module to activate the high-speed relay, allowing the fan to operate at full speed for rapid cooling. This design not only protects the engine from overheating damage but also saves fuel since it doesn't waste electricity at low speeds. In practical applications, relays are common failure points. I've encountered situations where the fan only operates at low speed but not high speed, and upon inspection, found burnt relay contacts. Poor circuit connections can also cause unstable fan operation, making regular cleaning of the fan and testing of circuit connections crucial, especially during summer long-distance driving when ensuring the proper functioning of the cooling system is vital.
