Parking Brake Control Valve

The yellow diamond-shaped knob (Fig.) on the auxiliary dash panel operates the parking brake control valve (park brake switch). Pulling the yellow knob applies the tractor parking brakes (spring brakes). Pushing in the knob releases the tractor parking brakes. Before the parking brakes can be released, the air pressure in either air brake system must be at least 65 psi (448 kPa).

Trailer Air Supply Valve (red knob)

Parking Brake Control Valve (yellow knob)

Fig. 1, Brake Valve Control Knobs

See General Information under the heading "Dual Air Brake System" for further information about the parking brake control valve.