Operator Cab and Controls - Section 32 3/10 OM3216 Page 32-40 AUTOMATIC RETARD SPEED CONTROL (ARSC) If any failure in the system occurs during operation, the alarm sounds and the central warning lamp will illuminate. The RCM will turn the ARSC system off. Use the retarder control lever and/or the brake pedal to stop the machine in a safe place. Turn the ARSC switch off and notify maintenance. Automatic Retard Speed Control (ARSC) automati- cally actuates the retard system to maintain the travel speed at a set speed controlled by the operator. This system is designed to make retarding easier and more constant.
For instance, if the ARSC is on, and the set speed is set to 20 km/h (12 mph), the ARSC system will auto- matically apply retarding effort to slow the truck. As the truck descends a grade and attempts to exceed 20 km/h (12 mph), the ARSC maintains the set speed without the operator having to use the brake pedal or manual retard lever. Set Speed Functionality When setting the ARSC, vehicle speed cannot be set to less than 10 km/h (6 mph). If the set speed is set while the truck is moving slower than 10 km/h (6 mph) the ARSC will default to 10 km/h (6 mph). Likewise, the set speed cannot be set higher than 60 km/h (37 mph).
If the set speed is set while the truck is moving faster than 60 km/h (37 mph), the set speed will default back to 60 km/h (37 mph). In all other instances, the speed will be set to the actual travel speed. Refer to the retarding capacity chart in the cab before setting the travel speed. If the set speed exceeds the maximum permissible speed on the chart, overheating and damage to the retarding system may occur. The time taken for the machine travel speed to match the set speed may differ according to the grade of the slope.
If the set travel speed is near a transmission shifting point or there is a change in the grade of the slope, the transmission may shift (up or down) even during retarding. When the ARSC is actuated on slippery road sur- faces, the wheels may lock. If this occurs, turn the ARSC system off and use the manual retard lever or brakes to safely control the truck. The ARSC system can be set in any gear range except N or R. The set speed will remain in memory when the ARSC switch and/or the key switch is turned to OFF. The only method for removing the set speed from the memory is to cancel it using the ARSC lever. Refer to (d, Figure 32-21).
The ARSC system will only apply retarding effort when the ARSC switch is on. If the switch is turned off during retarding, the set speed indicator and ARSC pilot lamp will turn off and the brakes will release. Cancelling And Changing The Set Speed The ARSC will only apply retarding effort when the accelerator pedal is not being depressed. If the accelerator is pressed while the ARSC system is on, the RCM will cancel the ARSC. The service brakes and the retarder lever will both continue to function while the ARSC system is on. Moving the lever to the cancel position (d, Figure 32- 21) for more than 1 second cancels the set speed. The set speed indicator will display a 0 when can- celled.
If it is desired to increase the set speed, depress the accelerator pedal to increase speed, and when the desired set travel speed is reached, press the set switch on the auto retarder (ARSC) set lever. The set travel speed will be changed to the new speed. The retard lever is more responsive when the ARSC system is on. Use small increments when moving the lever to avoid locking the brakes.