BENDIX TCH-003-002 User Manual
R-7 Modulating Valve
B-W Pc. No. 283036
Ford Part No. DOHA 2B431-A
2. The R-7 Modulating Valve performs four functions:
A. Modulates spring brake actuator applications should a failure occur in the service
brake system. If a loss of air should occur in the primary delivery circuit of the
Dual Brake Valve, the R-7 Modulating Valve exhaust air from the spring hold-off
cavity of the spring brake actuator, resulting in an application on that axle which
is proportionate to the braking on the other axles. If a loss of air should occur in
the secondary delivery circuit of the Dual Brake Valve, rear axle braking is
assured because the primary circuit supplies rear axle service brakes; therefore,
the Spring Brake Actuators will not be actuated.
Dual Brake Valve, the R-7 Modulating Valve exhaust air from the spring hold-off
cavity of the spring brake actuator, resulting in an application on that axle which
is proportionate to the braking on the other axles. If a loss of air should occur in
the secondary delivery circuit of the Dual Brake Valve, rear axle braking is
assured because the primary circuit supplies rear axle service brakes; therefore,
the Spring Brake Actuators will not be actuated.
B. Provides for quick release of the spring hold-off cavity of the Spring Brake
Actuators, allowing a fast application of the Spring Brake Actuators.
C. Limits hold-off pressure to the Spring Brake Actuators. This hold-off pressure can
be adjusted by the adjusting screw on the Modulating Valve.
D. Prevents compounding of push rod forces when the Spring Brake Actuators are
in the applied position.