Cooling Fan

The cooling fan operation is controlled by the IC. The cooling fan receives a power supply via a 10A mini fuse in the CJB. Three additional wires connect the fan to the IC; one for a fan Pulse Width Modulation (PWM) for fan speed, one for a monitor signal and a ground.

The IC monitors its internal temperature and also receives temperature information from the TS. If one or both of these temperatures exceeds a predetermined value, the IC operates the cooling fan.

The IC can control the speed of the fan motor and hence the air flow to both the cluster and the TS, via air ducting, by varying the PWM signal to the motor.

At temperatures of up to 40°C (104°F) the cluster operates the fan motor speed at a duty cycle of 30%. as the temperature increases, the duty cycle is increase linearly up to a 100% duty cycle at temperatures of 60°C (140°F).

The monitor connection between the fan and the IC is used by the cluster to detect fan faults (for example a blockage). Any faults are recorded as a Diagnostic Trouble Code (DTC) in the IC.

When the TS requires cooling a request is sent from the TS on the MS CAN body bus to the IC. The IC uses the information from the TS to operate the fan at the required speed using PWM.

If the TS or the IC are individually requesting cooling fan operation, the fan request is granted for that components requirements. If both the TS and the IC both request fan operation, the fan duty cycle is set to operate to the greater of the two requests.