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FEATURES
5.11.6
VARIABLE SPEED FAN (FAN TYPE 3) WITHOUT FAN SPEED
FEEDBACK
DDEC VI uses a pulse width modulated (PWM) output to drive a variable speed fan. The fan may
be enabled by speci
fi
c engine temperature sensors and various other inputs. The fan will ramp up
to the requested speed in order to reduce noise, shock-loading, and belt slippage. If the fan is
turned on for any reason other than high temperature, it will ramp up to the full fan speed (i.e. 5%
or 10% duty cycle, application dependent). A decrease in fan speed will occur after a short time
delay and will step down to the value dictated by the highest sensor request. If the A/C switch is
opened, the fan will increase speed at the ramp rate until it is at a maximum. After the A/C switch
is grounded the fan will remain on for a short time delay and then turn off.
NOTE:
Fan output circuits are designed to sink no more than 2.0 A (DC) current.
The PWM output is initiated when at least one of the following conditions occur:
□
Intake manifold or coolant temperatures above factory set limits
□
Air conditioner is active (OEM supplied A/C switch is opened) – optional
□
Intake manifold or coolant temperature sensor fails
□
Fan Control Override Switch is grounded (ON)
□
PTO is enabled and active – optional
5-68
All information subject to change without notice.
(Rev. 01/07)
7SA827 0701
Copyright © 2007 DETROIT DIESEL CORPORATION