Radiator Cooling Fan Motor Relay: Description and Operation

DESCRIPTION

8w-90-10:

Radiator 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 Control Module (BCM)
- Vehicle speed
- Transmission oil temperature

The PCM uses these inputs to determine when the fan should operate and at what speed.