OM3223 Operation - Section 32
Operator Cab and Controls Page 32-3
SERVICE BRAKE PEDAL
Service brake pedal (2, Figure 32-4) is a foot-oper-
ated pedal which applies the service brakes.
NOTE: In some optional installations, this pedal may
not be present, because it is incorporated into a
single pedal function with retarder pedal (3).
DYNAMIC RETARDER PEDAL
Dynamic retarder pedal (3, Figure 32-4) is a foot-
operated pedal which allows the operator to slow the
truck and maintain a safe productive speed without
the use of the service brakes. For normal truck oper-
ation, only dynamic retarding is to be used to slow
and control the speed of the truck. Grade/speed
chart (8, Figure 32-1) is to be followed to determine
maximum safe truck speeds for descending various
grades with a loaded truck. Service brakes are to be
applied only when dynamic retarding requires addi-
tional braking force to slow the truck speed quickly
and to bring the truck to a complete stop.
When dynamic retarding is in operation, the engine
rpm will automatically go to an advance rpm retard
speed setting (usually 1250 RPM)*. Dynamic retard-
ing will be applied automatically, if the speed of the
truck reaches the predetermined overspeed retard
setting. Dynamic retarding is available in forward/
reverse at all truck speeds above 0 kph/mph, but is
available in NEUTRAL only when truck speed is
above 4.8 kph (3 mph).
* NOTE: The exact engine speed in retarding may
vary (1250 - 1650 rpm) due to the temperature of
certain components; this is controlled by the Statex III
control system.
Optional - Dual Function / Single Pedal
The dynamic retarding/brake pedal is a single foot-
operated pedal which controls both retarding and
service brake functions. Thus, the operator must first
apply, and maintain, full dynamic retarding in order to
apply the service brakes.
When the pedal is partially depressed, the dynamic
retarding is actuated (actuation is modulated). As the
pedal is further depressed, dynamic retarding is fully
applied; then, while maintaining full retarding, the
service brakes are actuated (a slight increase in
pedal resistance will be felt) through a hydraulic
valve, which modulates pressure to the service
brakes. Completely depressing the pedal causes full
application of both dynamic retarding and the service
brakes.
THROTTLE PEDAL
Throttle pedal (4, Figure 32-4) is a foot-operated
pedal which allows the operator to control engine
rpm, depending on pedal angle.
HEATER / AIR CONDITIONER VENTS
The operator has complete control of the air flow in
the cab. Heater/air conditioner vents (5, Figure 32-1)
are flapper type which may be individually opened or
closed and may be rotated 360° for optimum air flow.
There are four (three not shown) across the top of
the panel, two in front of the operator (one each in
right and left panel modules), and four below the
panel.
FIGURE 32-4. PEDALS
1.Cab Floor
2.Service Brake Pedal
3.Retarder Pedal
4.Throttle / Accelerator
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