FORD 2013 F-550 v.1 - Manual (Page 229)

Whether accelerating or decelerating, once the desired descent speed is
reached, remove your feet from the pedals and the chosen vehicle speed
will be maintained.
Note: Noise from the ABS pump motor may be observed during hill
descent control operation. This is a normal characteristic of the ABS and
should be no reason for concern.
Hill descent modes
• At speeds below 20 mph (32 km/h): When the HDC switch is pressed
and HDC is active, the HDC telltale will flash.
• At speeds below 20 mph (32 km/h): When the HDC switch is pressed
and conditions are not correct for hill descent activation, the HDC
system will be enabled, the light in the cluster will be on solid and
HILL DESCENT CONTROL READY will be displayed in the message
center.
• At speeds above 20 mph (32 km/h): When the HDC switch is pressed,
the HDC system will be enabled, the light in the cluster will not be
illuminated and FOR HILL CNTRL, 20 MPH OR LESS will be displayed
in the message center.
Refer to Message center in the Instrument Cluster chapter for hill
descent control messages.
228 Terrain Response
2013 F-250/350/450/550 (f23)
Owners Guide gf, 1st Printing
USA (fus)