Honda Pilot: 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 A/C condenser relay to the ON position. Then, current flows from the 12 volt battery to the A/C condenser fan relay, the A/C condenser fan motor, the fan control relay and the radiator fan motor, to create a series connection through the A/C condenser fan motor and the radiator 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 FAN LO terminal and FAN HIGH terminal. This switches the A/C condenser fan relay, the fan control relay, and the radiator fan relay to the ON position. With the A/C condenser fan relay and the 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 and then through the fan control relay to the ground. This rotates the A/C condenser fan at a high speed. In addition, with the radiator fan relay and the fan control relay in the ON position, current from the 12 volt battery flows through the radiator fan relay to the radiator fan motor to the ground. This rotates the radiator fan at a high speed.

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