Parking Brake Control Valve
Note: See Brake System General Information for detailed information about brake systems.
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 both the tractor and the trailer spring parking brakes. Push the knob 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, 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)