Driver Controls on the right-hand control panel. See Fig. 4.25 . Pressing the switch will temporarily allow more drive wheel spin. Pressing the switch again will cause the system to go back to normal operation. 1 2 03/10/99 f610291 1. Trailer Air Supply Valve (red knob) 2. Parking Brake Control Valve (yellow knob) Fig. 4.24, Brake Valve Knobs Trailer Air Supply Valve The trailer air supply valve charges the trailer air supply system and releases the trailer spring parking brakes. See Fig. 4.24 , Item 1. Pull the trailer air supply valve out before disconnect- ing a trailer or when operating a vehicle without a trailer. 05/15/2001 f610494 Fig.
4.25, ATC Switch Trailer Brake Lever The trailer brake lever, located on the right-hand side of the steering column is used for applying the trailer service brakes without applying the truck or tractor service brakes. See Fig. 4.7 , Item 6. The valve can be partially or fully applied, but in any partially-on position it will be overridden by a full application of the service brake pedal. Moving the lever down ap- plies the trailer brakes, while moving it up releases the trailer brakes. The lever will automatically return to the up position when it is released. NOTICE The ATC option is intended to be used under specific slippery conditions that require momen- tary increased wheel spin.
Using this option for an extended period of time may damage the ve- hicle brake system. Adjustable Steering Column Controls Antilock Braking System Adjust the seat to the desired ride position, then tilt or telescope the steering column as needed using the steering column lever in Fig. 4.7 . The Meritor WABCO® Antilock Braking System (ABS) controls wheel speed during emergency stops or wheel lock situations. To tilt the steering column, pull the lever up toward the driver. Tilt the wheel to the desired position and release the lever. During emergency or reduced-traction stops, fully depress the brake pedal until the vehicle comes to a safe stop. Do not pump the brake pedal .
With the brake pedal fully depressed, the ABS will control all wheels to provide steering control and a reduced braking distance. To telescope the steering column, push the lever down (away from the driver) and pull or push the steering wheel to the desired position. Release the lever to lock the steering column in place. Vehicles with ABS may have Automatic Traction Con- trol (ATC). The ATC system automatically limits wheel spin during reduced-traction situations. If the vehicle has ATC, there will be an ATC switch located 4.12