Radiator Fan Relay
DESCRIPTIONRadiator Fan Relay:
The radiator fan relay is a solid state type and is located under the left front headlamp module.
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 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:
^ Engine coolant temperature
^ A/C pressure transducer
^ Ambient temperature from the body controller
^ Vehicle speed
^ Transmission oil temperature
The PCM uses these inputs to determine when the fan should operate and at what speed.