Grand Caravan V6-3.8L VIN L (2007)
Radiator Cooling Fan Motor Relay: Description and Operation
Operation
GAS ENGINES
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 30% 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.
