TM 9-2320-363-20-1
Section 4
TROUBLESHOOTING CHARTS
D. CHART 25 - FAN CONTROL MALFUNCTION (Cont'd)
Variable Speed Single Fan with PWM Control
The single fan uses the PWM signal to drive a variable speed fan. The PWM signal is controlled by two of three
temperature sensors. The fan can be turned "on" by either temperature sensor. The sensor requesting the highest fan
speed is used. The fan is off when the duty cycle of the PWM signal is 100%. The highest speed of the fan is produced
when the duty cycle is 0%. The fan speed will ramp up to the speed requested over a span of 10% Duty Cycle/sec. The
decrease in fan speed will occur after a short time delay and will step down to the value dictated by a sensor or off.
The PWM when at least one of the following conditions occur.
1.
Coolant Temperature above 118 C
2.
Intercooler Temperature above 180 C
3.
Oil Temperature above 118 C
4.
Air conditioner is active (OEM supplied A/C switch is opened)
Note: The temperature values used above are default values. These values can be changed at the time of
engine order.
Digital Inputs and Outputs
The following is a list of digital inputs and Outputs that are used with Fan Control:
Digital Inputs:
Air Conditioner Status
Fan Control Override
Outputs:
Fan Control 1
Fan Control 2
PWM Output
Change 3 3-345.173
