10.8
FAN OPERATIONAL CONCERN (ON/OFF TYPE)
10.8 FAN OPERATIONAL CONCERN (ON/OFF TYPE)
This section covers only the DDEC controlled fan operation, (fan type single, dual or two-speed).
If the function is assigned, see description of DDEC fan control logic, listed in Table 10-6.
Cavity
Wire#
Function
Output/Input
X#
#
Fan Control 1
Output - Required
X#
#
Aux. Fan Control
Input - Optional
X#
#
Fan Override
Input - Optional
Table 10-6
DDEC Fan Control Logic Description
10.8.1
Digital Fan Operation
Items used in digital fan operation include:
1. The ECM provides ground (output Fan Control 1) and should be wired such that when this
cavity grounds, the fan should turn off. When the circuit goes open, the fan should turn on.
2. When Aux. Fan Control is configured (input), this wire must be connected to battery
ground, or the fan will always be on. Typically, this is used with an air conditioning
pressure switch. High pressure opens this circuit, and turns the fan on for a minimum time
that can be set with the programming station on later ECM software versions.
3. Fan Override - Grounding this wire will turn the fan on. This would normally be an
OEM supplied switch on the dash.
Other than these items, the ECMs fan control output opens, turning the fan on due to engine
temperatures that are above the programmed limits. Once a fan output turns the fan on for
whatever reason, all fan off temperatures must be met before the fan will turn off.
Temperatures for most highway applications are listed in Table 10-7.
Fan Control
Actual Fan Status
Coolant Temp
Oil Temp
Air Temp
Fan Control - 1
Fan ON
96
C / 204
F
110
C / 230
F
66
C / 150
F
Fan Control - 2
Fan ON
98
C / 208
F
113
C / 235
F
N/A
Fan Control -
Fan OFF
92
C / 197
F
104
C / 219
F
49
C / 120
F
Table 10-7
Highway Application Temperatures
These temperature limits are only changeable in the base calibration.
10.8.2
Check Output Status
Perform the following steps to troubleshoot a fan operation problem:
1. Start engine.
All information subject to change without notice.
10-36
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION
