SERVICE MANUAL
Fig. 5 Typical Air System Schematic with Modular
Control Valve
1Exhaust Port
2Spring Brake Chamber
3Delivery-Tractor Port
4Auxiliary Air Delivery
5Secondary Reservoir
6Reservoir #2 Supply Port
7Reservoir #1 Supply Port
8Primary Reservoir
9Delivery-Trailer Port
10Tractor Protection Valve
The parking brake valve (yellow knob) controls the
spring brakes on the tractor and when exhausted,
simultaneously causes the trailer supply valve to trip and
exhaust, thus applying both tractor and trailer parking
brakes as required by Federal Regulations. The trailer
brakes may be independently released by pushing only
the trailer air supply valve (red knob) in.
OPERATION
Initial Charge
With the system completely discharged, both knobs
are out (Fig. 6). When system pressure reaches 448
kPa (65 psi), the red knob (trailer supply) may be pushed
in (Fig. 7) and should stay in, charging the trailer system
and releasing the trailer brakes. The yellow knob (system
park) may now be pushed in (Fig. 8 ) which will supply air
to the tractor spring brakes, releasing them.
System Park (Fig. 6)
With both knobs in for normal tractor-trailer, run
modes, the parking brakes on, both tractor and trailer’
may be actuated by pulling the yellow knob out, which
exhausts the air from the tractor spring brakes and
simultaneously causes the trailer supply valve to pop out,
applying the trailer brakes. This complies with Federal
Regulations that one control must apply all the parking
brakes on the vehicle.
Fig. 6 Total Vehicle Parked
Fig. 7 Charge Trailer with Tractor Parked
Legend for Figs. 6, 7, 8 & 9
1Trailer Supply
2Parking (Spring) Brake
3Modular Control Valve
4Trailer Emergency
5Tractor Protection Valve
6Trailer Emergency
7Quick Release Valve
8Spring Brake Chamber
9Tractor Spring Brake Control
10Secondary Reservoir
11Primary Reservoir
12Exhaust
CTS-4079 - CHAPTER VII - Page 7
