Electric Cooling Fan
The engine cooling fan control module is provided with:
- Power supply from the Battery Junction Box (BJB).
- Ignition signal from the Powertrain Control Module (PCM) relay in the BJB.
- PCM control signal.
- Ground.
The system is protected against abnormal internal temperature by measuring its internal temperature at 2 points with temperature sensors.
- Sensor 1: This sensor is used to calculate the temperature of active components near the micro controller. When the internal temperature reaches 135°C (275°F), the electric cooling fan stops immediately. After motor stops, after a delay of 120 seconds, the diagnostic feedback is sent. Normal operation resumes when the temperature is less than 120°C (248°F).
- Sensor 2: This sensor is used to measure the temperature of the power stage of the Printed Circuit Board (PCB) to reduce the power. When the temperature is too high, the sensor stops the motor to prevent an over temperature condition.
The electric cooling fan will derate when the powerstage internal temperature reaches 135°C (275°F), and stop the motor function at 145°C (293°F). After the motor stops, after a delay of 120 seconds, the diagnostic feedback is sent. Normal fan operation resumes when the powerstage temperature falls to 135°C (275°F).
The PCM gets the signals from the engine coolant temperature sensor and the HVAC control module (HVAC). Then the PCM determines when to operate the electric cooling fan. The PCM also adjusts the electric cooling fan demand to compensate for the ram effect of vehicle speed.
The PCM signals to the engine cooling fan control module between 0 and 100%. This operates the electric cooling fan motor in 1 of 4 modes:
- OFF
- Minimum speed
- Linear variable speed between minimum and maximum speeds
- Maximum speed.
In hot operating conditions, the electric cooling fan may continue to operate for up to 5 minutes after the engine has been switched OFF.
The electric cooling fan control module monitors for over and under input voltage, a stalled motor and a partially stalled motor. In case of any faults detected, the electric cooling fan control module temporarily sends the signal to ground. The length of time, the signal goes to ground varies between 2 seconds and 8 seconds, depending on the fault. The electric cooling fan control module repeats the notification process at 5 second intervals until the fault is cleared. When there is more than 1 fault, only the highest priority fault is notified to the PCM.
The fault priorities in descending order are the following:
- Over voltage
- Under voltage
- Stalled motor
- Partially stalled motor.
The PCM records a related Diagnostic Trouble Code (DTC) for faults notified by the engine cooling fan control module. Then the PCM sends the signals to the Body Control Module/Gateway Module (BCM/GWM) through the FlexRay. The BCM/GWM transmits the signal through the HS CAN comfort systems bus to the Instrument Cluster (IC) to display a warning message.
The nominal operating voltage for the electric cooling fan is from 9V to 16V. When the input voltage is outside of the limits, the engine cooling fan control module stops operation of the electric cooling fan. In addition the electric cooling fan control module notifies the PCM of the fault. After an under or over voltage occurs, the electric cooling fan operation resumes when the input voltage increases to 9.5V, or decreases to 15.5V, respectively.
Each time, 2 seconds after the electric cooling fan starts, the electric cooling fan control module checks the electric cooling fan motor speed. When the speed is 0, the electric cooling fan control module determines the electric cooling fan motor has stalled and tries a restart. For a restart, the electric cooling fan control module disconnects the power from the electric cooling fan motor. Then the electric cooling fan control module immediately reconnects the power at an increased current level.
The electric cooling fan control module tries up to 6 restarts of a stalled motor, increasing the output current each time. When the electric cooling fan motor remains stalled after the 6 times restart, the electric cooling fan control module waits 40 seconds. Afterwards the electric cooling fan control module notifies the PCM of the fault and begins the start process again.
The electric cooling fan control module incorporates a temperature sensor to prevent damage caused by excessive heat at high ambient temperatures. Operation of the electric cooling fan control module STOPS when the temperature reaches 135°C (275°F). Operation resumes when the temperature decreases to 120°C (248°F).