Bendix Commercial Vehicle Systems M-12R ANTILOCK MODULATOR - Manual

1
®
SD-13-4772
Bendix ® M-12 ™ & M-12R ™ AntiLock Modulator
designed for direct controller mounting while the M-12R ™
modulator uses a cover plate where the controller would
normally mount and a wire harness is attached to the
M-12R
™ modulator in order to connect it to the antilock
controller. Two body styles are available; one with four
vertical delivery ports and another with two vertical and two
horizontal delivery ports.
The M-12 ™ /M-12R ™ modulator is normally mounted close
to the service actuators it serves, and it can be nipple
mounted to a reservoir or secured to the frame rail.
The M-12 ™ modulator air connections are as follows:
M-12 ™ /M-12R ™ Modulator Embossed
Air Connection Identification
Supply (to reservoir) SUP
Delivery (to brake actuator) DEL
(can have 2 horizontal & 2
vertical deliveries or
4 vertical deliveries)
Control
CON
(to rear service brake valve delivery)
The standard M-12 ™ and M-12R ™ modulator is offered with
a 4 psi crack pressure. The internal components are
interchangeable with R-12
™ and R-14 ™ relay valves therefore,
the same maintenance kit is used to service all.
DESCRIPTION
The M-12 ™ antilock modulator is a standard component in
Bendix antilock systems. It is comprised of two components:
solenoids, which rapidly apply and exhaust air during an
antilock stop, and a standard relay valve.
During normal, non-antilock operation, the M-12 ™ modulator
serves as a relay valve that speeds the application and release
of the service brakes. If wheel lock up is impending, a antilock
controller commands the solenoids to modulate brake
chamber pressure on the axle(s) on which the system is
installed.
The M-12 ™ modulator is offered in two configurations as
illustrated in figure 1. The M-12 ™ modulator permits direct
attachment of an antilock controller, and it accepts electronic
commands from the controller through a four pin connector
(see Figure 1). The M-12R
™ modulator is designed for remote
mounting on a vehicle frame rail or cross member. It accepts
electronic commands from a remote mounted controller
through a wire harness assembly that has a four pin
connector at one end and a three pin connector at the other
(see Figure 1). The M-12
™ modulator and M-12R ™ modulator
differ from each other only in that the M-12 ™ modulator is
FIGURE 1 M-12 ™ AND M-12R ™ MODULATORS
M-12 ™ Modulator M-12R ™ Modulator
CONTROL
PORT
3 PIN
CONNECTOR
CONTROL
PORT
WIRE
HARNESS
4 PIN
CONNECTOR
SUPPLY
PORT DELIVERY
PORTS
2 VERTICAL
2 HORIZONTAL
SUPPLY
PORT
DELIVERY
PORTS
4 VERTICAL
COVER
PLATE