Medium Duty Operator's Manual - Peterbilt Motors Company

STARTING AND OPERATING THE VEHICLE
• During the time it takes you to drink a cup of coffee,
your engine can cool as much as 60° F (33° C) below
normal operating temperature. To keep the engine
warm during a short break, turn it off. Do not allow
your engine to idle longer than five minutes.
Engine Fan Switch (Option)
Your Medium Duty may have an engine fan switch
installed as an option. The switch, which is mounted on
the accessory switch panel, allows you to control the
engine fan manually or automatically.
• With the ignition key switch ON and the fan switch in
the ON position, the engine fan will be on regardless
of engine temperature.
• With the engine fan switch in the AUTOMATIC position,
the engine fan will automatically turn on when
the engine coolant reaches a temperature of about
200°F (93°C)
WARNING! Do not work on or near the fan
with the engine running. Anyone near the
engine fan when it turns on could be seriously
injured. If it is set at MANUAL, the fan will turn
on any time the ignition key switch is turned
to the ON position. In AUTO, it could engage
suddenly without warning. Before turning on
the ignition or switching from AUTO to MAN-
UAL, be sure no workers are near the fan.
CAUTION: The fan or equipment near it could
be damaged if the fan turns on suddenly when
you do not expect it. Keep all tools and equipment
away from the fan.
NOTE: Do not operate the engine fan in the MAN-
UAL position for extended periods of time. The
fan hub was designed for intermittent operation.
Sustained operation will shorten the fan hub's
service life as well as reduce fuel economy.
Cruise Control (Option)
This feature improves fuel mileage and reduces driver
fatigue by maintaining a constant vehicle speed. The
cruise control will only operate above a programmed minimum
vehicle speed, 15 mph for the CAT 3126B engine,
30 mph for the Cummins ISC engine.
– 94 – Y53-6008A Medium Duty (R05/09)