8-30
Published 01-14-2021 Control # 707-01
CARRIER
TMS9000-2 SERVICE MANUAL
Relay Valve
The purpose of the two piston operated relay valves
(Figure 8-21) is to speed up application of the service
brakes. The valve is remote mounted and delivers air to the
brakes in response to signals from the foot brake control
valves.
One valve is mounted on the front of the frame for front
service brakes and one is mounted on the rear of the frame
for the rear service brakes. Air pressure, which controls the
valve, enters through the service port to either deliver or
exhaust air pressure from the circuits serviced by the relay
valve.
Dual Brake Valve
The dual brake valve is a suspended, pedal operated brake
valve which has two separate supply and delivery circuits.
The valve is located under the front console to the right of the
steering column. The valve provides the driver with a
graduated control for applying the service brakes or the
parking brakes through the spring brake control valve.
Spring Brake Control Valve
The spring brake control valve (Figure 8-22) is located on the
rear of the carrier frame. The purpose of the valve is to
supply a specific, limited hold off pressure to the spring
brakes, and in the event of loss of primary pressure, to
modulate the spring brakes through use of the dual brake
valve.
Park Brake Control Valve
The park brake control valve is an on/off push/pull control
valve located on the front console. When the air pressure
reaches 340 kPa (50 psi) and the button is pushed in, the
park brakes are disengaged. The button will pop out when
the air pressure falls below 280 kPa (40 psi) exhausting the
delivery line and engaging the brakes.
Anti-lock Modulator
The quick release anti-lock system modulators are on/off air
valves that incorporate a pair of electrical solenoids for
FIGURE 8-21
1
2
3
Item
Description
1
Service Port
2
Supply Port
3
Delivery
FIGURE 8-22
1
2
3
4
Port
Designation
1
Air Supply Port
2
Air Delivery Port
3
Air Exhaust Port
4
Park Control Port
Fo
r
Reference
Only
