Dash-Mounted Brake Controls
Note: See Brake System Operation for detailed information about brake systems.
Parking Brake Control Valve
The yellow diamond-shaped knob on the dash operates the parking brake valve. See Fig.. Pull the knob out to apply both the tractor and the trailer spring parking brakes.
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Trailer Air Supply Valve (red knob)
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Parking Brake Control Valve (yellow knob)
Fig. 1, Brake Valve Control Knobs
Push both the yellow parking brake and the red trailer air supply knobs in to release the tractor and trailer spring parking brakes. Before the spring parking brakes can be released, the air pressure in either air brake system must be at least 65 psi (447 kPa).
If the trailer is not equipped with spring parking brakes, pulling the yellow parking brake valve out applies the tractor parking brakes and the trailer service brakes.
Trailer Air Supply Valve
The red octagonal-shaped knob operates the trailer air supply valve, which charges the trailer air supply system and releases the trailer spring parking brakes. See Fig..
After the vehicle and its air hoses are connected to a trailer and the pressure in the air system is at least 65 psi (447 kPa), push the red trailer air supply valve knob in (and leave it in) to charge the trailer air supply system and release the trailer spring parking brakes.
Pull the red trailer air supply valve out before disconnecting a trailer or when operating a vehicle without a trailer.
Trailer Brake Lever
The trailer brake lever is used to apply the trailer service brakes without applying the truck or tractor service brakes. It is usually mounted on the right-hand control panel. See Fig.. 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.
Move the lever down to apply the trailer brakes; move the lever up to release the trailer brakes. The lever will automatically return to the up position when it is released.
Fig. 2, Trailer Brake Lever
Antilock Braking System
The Antilock Braking System (ABS) passively monitors vehicle wheel speed at all times and controls wheel speed during emergency stops or wheel lock situations.
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.
The ABS is designed to communicate with a trailer ABS, if they are compatible. Compatibility will result in the illumination of the trailer ABS lamp during vehicle start-up and fault detection. The trailer ABS lamp will not illuminate unless a compatible trailer is connected to the tractor.
Vehicles with ABS may have Automatic Traction Control (ATC). On these vehicles, the ATC system automatically limits wheel spin during reduced-traction situations. In normal braking applications, the standard air brake system is in effect.
Toggling the ATC SPIN switch up, shown in Fig., shuts the ATC off and allows drive wheel spin.
Notice: The ATC spin feature is intended to be used under specific slippery conditions that require momentary increased wheel spin. Using this option for an extended period of time may damage the vehicle brake system.
Fig. 3, ATC SPIN Switch
Toggling the switch down, or cycling the ignition key, will cycle the system back to normal operation.