OM3020.2 12/99 Operation - Section 3 Operator Cab and Controls Page 3-15 DYNAMIC RETARDER CONTROL LEVER ACCELERATOR (THROTTLE) PEDAL The Dynamic Retarder Control Lever (6, Figure 3-2) mounted on the right side of the steering column can be used to modulate retarding effort. The lever will command the full range of retarding and will remain at a fixed position when released. The Accelerator Pedal/Throttle Pedal (4, Figure 3-1) is a foot-operated pedal which allows the operator to control engine RPM, depending on pedal depression. It is used by the operator to request torque from the motors when in Forward or Reverse.
In this mode, the propulsion system controller commands the correct engine speed for the power required. In Neutral, this pedal controls engine speed directly. a. When the lever is rotated to full “Up” (counter- clockwise) position, it is in the “Off/No Retard” position. b. When the lever is rotated to full “Down” (clock- wise) position, it is in the full “On/Retard” position. c. For long downhill hauls, the lever may be posi- tioned to provide a desired retarding effort, and it will remain where it is positioned. NOTE: The Retarder Control Lever must be ro- tated back to the “Off” position before the truck will resume the PROPEL mode of operation .
The lever and foot-operated Retarder/Service Brake pedal can be used simultaneously or independently. The Propulsion System Controller (PSC) will determine which device is requesting the most retarding effort and apply that amount. Starting On A Grade With A Loaded Truck DYNAMIC RETARDER/SERVICE BRAKE PEDAL Initial propulsion with a loaded truck should begin from a level surface whenever possible, but when there are circumstances where the starting on a hill or grade cannot be avoided, use the following procedure: The Dynamic Retarder/Service Brake Pedal (3, Figure 3-1) is a single, foot-operated pedal which controls both retarding and service brake functions.
The first portion of pedal travel commands retarding effort through a rotary potentiometer. The second portion of pedal travel modulates service brake pressure directly through a hydraulic valve. Thus, the operator must first apply, and maintain, full dynamic retarding in order to apply the service brakes. Releasing the pedal returns the brake and retarder to the “off” position. 1. Fully depress the foot-operated retarder/service brake pedal (do NOT use retarder lever) to hold the truck on the grade. With service brakes fully applied, move the selector switch to a drive posi- tion (Forward/Reverse) and increase engine RPM with throttle pedal.
When the pedal is partially depressed, the dynamic retarding is actuated. As the pedal is further depressed to where dynamic retarding is fully applied; the service brakes (while maintaining full retarding) are then actu- ated through a hydraulic valve, which modulates pres- sure to the service brakes. Completely depressing the pedal causes full application of both dynamic retarding AND the service brakes . An indicator light (B3, Figure 3-7) in the overhead panel will illuminate, and an increase in pedal resistance, will be felt when the the Service Brakes are applied. 2.
As engine RPM approaches maximum, and opera- tor senses propulsion effort working against the brakes, release the brakes and let truck move- ment start. Be sure to completely release the foot-operated retarder/service brake pedal. As truck speed increases above 3-5 MPH (5-8 KPH) the Propulsion System Control (PSC) will drop propulsion, if the retarder is still applied. Releasing and reapplying dynamic retarding dur- ing a hill start operation will result in loss of pro- pulsion and, if truck speed is above 1-2 mph, application of retarding effort. For normal truck operation, Dynamic Retarding (lever or foot-operated pedal) should be used to slow and control the speed of the truck.
HEATER / AIR CONDITIONER VENTS Service brakes should be applied only when dynamic retarding requires additional braking force to slow the truck speed quickly, or when bringing the truck to a COMPLETE stop. Each heater/air conditioner vent (5, Figure 3-1) is a flapper type which may be opened or closed or rotated 360° for optimum air flow. There are four (three not shown) across the top of the panel, one each in the right and left panel modules, and four below the panel.