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| Illustration 1 | g02022521 |
The "Automatic Retarding Control (ARC)" function is controlled by the Brake ECM. The "ARC" system allows the operator to maintain constant truck speed during long downgrades. The "ARC" also functions to maintain constant speed of the engine during long downgrades. The ARC also provides protection for the engine in overspeed conditions. The ARC system signals the Engine ECM to engage the Service brake.
The operator has the option of selecting the control point for the "Automatic Retarding Control (ARC)" of the machine as the machine descends a grade. Productivity is maximized because the control speed of the engine can be set to a lower value than the high idle speed.
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| Illustration 2 | g02012094 |
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The "Auto Retarder Control (ARC)" switches are at the base of the center console of the truck. (1) "Auto Retarder Control (ARC) ON/OFF" switch (2) "Auto Retarder Control (ARC) UP/DOWN" switch | |
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| Illustration 3 | g02022523 |
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Diagram of ARC ON/OFF switch | |
The "ARC ON/OFF" switch must be in the ON position for the machine operator to set the retarding speed of the machine.
Function of the "Retarder Control" Machine Speed Setting
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| Illustration 4 | g02022527 |
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The "Advisor" screen as ARC is being engaged for the truck. | |
The operator uses the "SET/ACCEL, DECEL" switch to implement this feature. The upper portion of the rocker switch serves as the "SET/ACCEL" function. The lower portion of the rocker switch serves as the "DECEL" function.
The operator sets the control point of the retarder control by depressing the "SET/ACCEL" (top) portion of the rocker switch. The retarding speed is now set to the corresponding EOS at that speed of the machine. The operator requested gear (top drive gear limit) is set to the gear that the transmission is at when the switch is pressed.
Note: The retarding speed for the machine can be set only when the throttle pedal is NOT DEPRESSED.
Retarder Control Machine Speed Accelerate/Decelerate Functionality
Once a valid retarder control speed for the machine has been successfully set, the operator can implement the "SET/ACCEL/DECEL" rocker switch to raise or lower the retarder control machine speed. The retarder control machine speed CAN ONLY be adjusted to a machine speed that corresponds to the maximum retarding speed of the engine. The speed of the engine must be ABOVE the corresponding downshift braking shift points for the setting of the gear.
For the speed limit to be successfully set, there must be some handshaking between the Transmission ECM and the Brake ECM. The Transmission ECM will perform all the logic related to the retarding control feature. The Transmission ECM will provide the Brake ECM with a control point for the ARC engine speed and a retarder point for the machine speed. The actual gear of the transmission must be greater than 2F to avoid any problems with the D position in the "Shift Lever Position" banner on the "Advisor" reporting a gear of less than 3. The Brake ECM will now set the new control point of the ARC and alert the "Advisor" to display the appropriate speed limit of the machine.