Ford F-650 2001 Owner's Manual page 122

Driving
Operation
Push the rocker switch up to turn
the exhaust brake on. The switch
will illuminate in the ON position.
Push the switch down to turn the
brake off.
Starting engine
Before starting the engine, make sure that the exhaust brake switch is in
the OFF position. Do not turn the exhaust brake on until the engine has
reached normal operating temperatures.
Driving downhill
While approaching a steep grade, make sure that the exhaust brake
switch is in the ON position. The exhaust brake actuates as soon as you
remove your foot from the accelerator pedal. While going down the
grade, use a low enough gear to descend safely with a minimum
application of the service brakes. As a general guideline, use the same
gear as you would to ascend the hill.
Before descending a hill or steep grade always select the proper gear. If
the transmission is taken out of gear while descending it is possible that
you will not be able to select another gear because of maximum RPM
being governed.
Make sure the engine speed does not exceed the maximum
allowable engine RPM. Exceeding the maximum allowable engine
RPM will result in damage to the engine. Apply the service brakes to
reduce the engine RPM or make a slower descent by using a lower
gear.
The exhaust brake is not recommended for use on slippery or
low traction road surfaces. Under these conditions a loss of
vehicle control could possibly occur.
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