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Cooling Fan Controls System Description - Overview
Overview
Receiving various signals, such as coolant temperature signals and refrigerant compression signals, from sensors, the PCM performs the fan control switching the fan speed (HI/LO) as needed. This control efficiently operates the radiator fan and A/C condenser fan, and improves fuel efficiency by reducing electrical load. Fan LO Control Operation
In fan LO control, the PCM switches the FANL terminal to the ON position, and that switches the radiator fan relay to the ON position. Then, current flows from the 12 volt battery to the radiator fan relay, radiator fan motor, fan control relay and A/C condenser fan motor, to create a series connection through the radiator fan motor and the A/C condenser fan motor. Using this series connection, the fan rotates at a lower speed. Fan HI Control Operation
In fan HI control, the PCM powers the FANL terminal and FANH terminal. This switches the radiator fan relay, fan control relay, and A/C condenser fan relay to the ON position. With radiator fan relay and fan control relay in the ON position, current from the 12 volt battery flows through the radiator fan relay to the radiator fan motor and then through the fan control relay to the ground. This rotates the radiator fan at a high speed. In addition, with A/C condenser fan relay and fan control relay in the ON position, current from the 12 volt battery flows through the A/C condenser fan relay to the A/C condenser fan motor to the ground. This rotates the A/C condenser fan at a high speed. |