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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 FAN LO 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, and that completes a series connection between the radiator fan motor and A/C condenser fan motor, and thus, the fan rotates at a low speed. Fan HI Control Operation
In fan HI control, the PCM switches the FAN LO terminal and FAN HI terminal to the ON position, and that switches the radiator fan relay and A/C condenser fan relay to the ON position. At the same time, the fan control relay switches to the ON position, therefore current from the 12 volt battery flows in two different directions, the first direction is to the radiator fan relay, radiator fan motor and fan control relay, and another is to the A/C condenser fan relay and A/C condenser fan motor, and that completes a parallel connection between the radiator fan motor and A/C condenser fan motor, and thus, the fan rotates at a high speed. |