Cooling Fan - Operation

OPERATION

STANDARD COOLING FAN STRATEGY





The radiator cooling fan used on the engines replaces the engine driven mechanical fan and the hydraulically controlled fan. This provides cooling at 350 watts to the light duty cooling systems on the vehicles. Helps in reducing unnecessary power drain on both the engine and the vehicles electrical system while keeping the NVH of the fan low.

The cooling fan is controlled by the PCM. A ground signal from the PCM is provide for the LOW fan relay. If the conditions are required for additional cooling. The PCM provides a ground to the HIGH relay.

There are three inputs to the PCM that determine what speed percentage of fan is required by the vehicle. These inputs are:

- Engine Coolant Temperature
- Transmission Oil Temperature
- A/C System Pressure

By monitoring these three parameters, the PCM can determine if cooling airflow is required. If airflow is required, the PCM will ground the required fan relay until the parameter(s) are under control. Once the temperature is reduced to within operating parameters the fan will ramp up or ramp down to maintain the temperature requirements.

MAX COOLING FAN STRATEGY





The radiator cooling fan used on the engines replaces the engine driven mechanical fan and the hydraulically controlled fan. This provides max cooling at 850 watts to the vehicles that require the additional cooling.

The radiator cooling fan is controlled by the PCM. A PWM (Pulse With Modulated) signal from the PCM controls the fan speed.

There are three inputs to the PCM that determine what speed percentage of fan is required by the vehicle. These inputs are:

- Engine Coolant Temperature
- Transmission Oil Temperature
- A/C System Pressure

By monitoring these three parameters, the PCM can determine if cooling airflow is required. If airflow is required, the PCM will send a signal to the fan module to slowly ramp up (speed up) the fan speed until the parameter(s) are under control. Once the temperature is reduced to within operating parameters the fan will ramp up, ramp down, or hold its speed to maintain the temperature requirements, while reducing unnecessary power drain on both the engine and the vehicles electrical system and keeping the NVH of the fan low.

ACTIVATING THE FAN WITH THE SCAN TOOL

Under the Engine Systems test heading, there is a subheading. "Fan solenoid test", that has the selections, on/off. Activating the fan with the scan tool will run the fan at a limited 72% duty cycle, which will help troubleshoot any system problems, and also help with the deaeration procedure.

NOTE: Engine doesn't need to be running to activate the fan with the scan tool.