1
Supply Port
(cast in 1, SUP)
Delivery Port
(cast in 2, DEL)
Exhaust Port
(cast in 3, EXH)
Electrical Connector
Mounting Holes
(.33" diameter thru body)
M-30
™
Modulator
FIGURE 1: M-30
™
MODULATOR
®
SD-13-4830
DESCRIPTION
The Bendix
®
M-30
™
modulator replaced both the M-21
™
(Figure 2) and M-22
™
(Figure 3) modulators in all applications.
The M-30
™
antilock system modulator (Figure 1) is a high
capacity, on/off air valve that incorporates a pair of electrical
solenoids for control. The solenoids provide the electro-
pneumatic interface between the antilock controller
electronics and the air brake system. The modulator is
used to control the braking function on individual or dual
service actuators during antilock activity. When used to
control both service chambers on an axle or two chambers
on the same side of a tandem axle, the modulator is
sometimes mounted ahead of a quick release valve, which
provides quick exhaust of service applications during normal
braking (Figure 4). In the case of individual wheel control
applications, the modulator is always the last control valve
through which air passes on its way to the service brake
actuator.
The modulator consists of a die cast aluminum body and a
solenoid assembly which contains one normally open
solenoid, one normally closed solenoid, and an inlet and
exhaust diaphragm valve. A three pin, weather resistant
electrical connector is an integral part of the modulator
solenoid assembly and serves to carry control commands
from the antilock controller to the modulator. Two mounting
holes are provided for frame or cross member mounting of
the valve.
FIGURE 2: M-21
™
MODULATOR
FIGURE 3: M-22
™
MODULATOR
Bendix
®
M-30
™
AntiLock Modulator Assembly
Mounting
Holes
Supply Port
(cast in 1)
Delivery Port
(cast in 2)
Exhaust
(cast in 3)
Solenoid
Connector
Mounting
Holes
Supply Port
(cast in 1)
Solenoid
Connector
Delivery Port
(cast in 2)
Exhaust
(cast in 3)
