Method and electronic device for controlling engine fan

In a heavy load bearing motor vehicle having an engine, a coolant system, an air conditioning system, a fan and a fan clutch, an analogue electronic fan control circuit comprising:

• heat sensing means for detecting the temperature of said coolant and generating a coolant temperature signal proportional thereto;
• first temperature signal generating means in electrical contact with said heat sensing means for receiving the coolant temperature signal and generating a first temperature signal when the coolant temperature exceeds a first selected temperature;
• second temperature signal generating means in electrical contact with said heat sensing means for receiving the coolant temperature signal and generating a second temperature signal when the coolant temperature exceeds a second selected temperature;
• speed sensing means for detecting the motor vehicle road speed and generating a speed signal proportional thereto;
• load sensing means for detecting the operation of said air conditioning system and generating a corresponding load signal;
• first override signal generating means in electrical contact with said heat sensing means for receiving the coolant temperature signal and generating a first override signal when said heat sensing means malfunctions;
• second override signal generating means in electrical contact with said speed sensing means and said load sensing means for receiving said speed and load signals and generating a second override signal when the vehicle road speed is less than a selected speed and the air conditioning system is engaged;
• control signal generating means in electrical contact with said first and second temperature signal generating means and said first and second override signal generating means for receiving and distinguishing input signals, including said first and second temperature signals and said first and second override signals and generating a control signal in response to at least one of said input signals operative to engage and drive the fan at a constant speed, such that the required engine cooling is achieved.

A method of electronically controlling an engine fan in a heavy load bearing vehicle having an engine, an engine coolant system, an air conditioning system and a fan, comprising the steps of:

• detecting the temperature of said engine coolant;
• generating a coolant temperature signal proportional to said coolant temperature;
• comparing the coolant temperature signal to a first selected temperature;
• generating a first temperature signal when the coolant temperature exceeds said first selected temperature;
• comparing said coolant temperature signal to a second selected temperature;
• generating a second temperature signal when said coolant temperature exceeds said second selected temperature;
• detecting the road speed of said motor vehicle;
• generating a speed signal proportional to said vehicle speed;
• detecting whether said air conditioning system is engaged;
• generating a load signal corresponding to the air conditioning system load on said engine;
• comparing said speed signal to a selected speed;
• generating an override signal when said vehicle speed is less than said selected speed and said air conditioning system is operating;
• providing control signal generating means for receiving and comparing input signals, including said first and second temperature signals and said override signal;
• and
• generating a control signal in response to at least one of said input signals operative to engage and drive the fan at a constant speed such that the required engine cooling is achieved.