Pacifica V6-3.8L VIN L (2005)
Radiator Cooling Fan Motor Relay: Description and Operation
RADIATOR FAN RELAY
DESCRIPTION
The radiator fan relay is a solid state type and is located on the back of the bumper beam. Refer to WIRING DIAGRAMS for a circuit schematic.
OPERATION
The solid state radiator fan relay is controlled by the Powertrain Control Module (PCM) by way of a Pulse Width Modulated (PWM) signal. The relay
control circuit supplies a 12 volt signal to the PCM. The PCM then pulses the ground circuit to achieve fan on time. The relay provides a voltage to
the fan motors which is proportional to the pulse width it receives from the PCM. The duty cycle ranges from 50% for low speed operation, then
ramps-up to 100% for high speed operation. This fan control system provides infinitely variable fan speeds, allowing for improved fan noise, A/C
performance, better engine cooling, and additional vehicle power.
To control operation of the relay, the PCM looks at inputs from:
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Engine coolant temperature
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A/C pressure transducer
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Ambient temperature from the body controller
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Vehicle speed
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Transmission oil temperature
The PCM uses these inputs to determine when the fan should operate and at what speed.