Detroit Diesel DDEC VI Application And Installation page 284

FEATURES
5.11.7 VARIABLE SPEED FAN (FAN TYPE 2) WITH FAN SPEED
FEEDBACK
DDEC VI uses a pulse width modulated (PWM) output to drive a variable speed fan. The fan may
be enabled by specific 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
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All information subject to change without notice. (Rev. 01/07)
7SA827 0701 Copyright © 2007 DETROIT DIESEL CORPORATION