Brake Controls
Note: See General Information for detailed information about brake systems.
Parking Brake Control Valve
Notice: Do not step on the service brake pedal while the parking brakes are applied. To do so can cause damage to the brake mechanisms.
The yellow diamond-shaped knob operates the parking brake valve. See Fig.. Pull the knob out to apply the tractor and the trailer spring parking brakes. Push the knob in to release the 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, pull the parking brake valve out to apply the tractor parking brakes and the trailer service 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
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 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 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
Engine Brake Switch
The Hi/Med/Lo engine brake 3-position switch controls the amount of engine braking. Press the lower third of the switch for low, center for medium, and upper third for high. See Fig..
