D. CHART 25 - FAN CONTROL MALFUNCTION
NOTE - This chart is only to be used if:
1) All basic mechanical checks and physical inspections have been performed with no problem found,
2) Diagnosis of DDEC-III was started at step Start-1, pg 3-345.41 and you have now been referred here.
DDEC III provides fan controls for three different fan configurations, in accordance with the proposed Truck Maintenance
Council (TMC) standards.
Two separate fans.
Two speed fans.
Single Fan with Digital Outputs
The single fan control uses one digital output to drive a single speed fan. Table 1 shows the input and output states
during fan operation. The digital output is called Fan Control 1. Fan Control 1 is opened to turn the fan "on". Fan Control
1 is switched to battery ground to turn the fan "off'.
Fan Control 1 is enabled (opened) when at least one of the following conditions occur.
Oil temperature above 111 C
Coolant temperature above 90 C
Air temperature above 49 C
Air conditioner is active (OEM supplied A/C switch is opened)
Oil temperature sensor fails
Coolant temperature sensor fails
Air temperature sensor fails
Fan engine brake enabled and the engine brake is active at "High" level.
Fan control override switch is enabled.
Pressure governor system is active,
Note: The temperature values used above are defaults values. These values can be changed at the time
of engine order.
Change 3 3-345.169