User's Manual

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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

Summary of content (12 pages)

PAGE 1
SD-13-4772 ® Bendix® M-12™ & M-12R™ AntiLock Modulator 4 PIN CONNECTOR SUPPLY PORT DELIVERY PORTS 2 VERTICAL 2 HORIZONTAL CONTROL PORT COVER PLATE DELIVERY PORTS 4 VERTICAL SUPPLY PORT WIRE HARNESS CONTROL PORT 3 PIN CONNECTOR M-12™ Modulator M-12R™ Modulator FIGURE 1 M-12™ AND M-12R™ MODULATORS DESCRIPTION The M-12™ antilock modulator is a standard component in Bendix antilock systems.
PAGE 2
SERIAL LINK DASH LAMP RELAY SPRING BRAKES SERVICE BRAKE RETARDER DISABLE IN-AXLE WHEEL SPEED SENSOR M-21™/M-22™ MODULATOR BRAKE VALVE STOP LIGHT SWITCH WS-20™ WHEEL SPEED SENSOR NOTCHED HUB EXCITER M-12™ MODULATOR WITH ANTILOCK CONTROLLER MOUNTED REAR AXLE (S) FRONT AXLE FIGURE 2A FULL VEHICLE AXLE CONTROL - TRUCK/TRACTOR NOTCHED HUB EXCITER SPRING BRAKES WS-20™ WHEEL SPEED SENSOR M-12R™ MODULATOR SR-5™ TRAILER SPRING BRAKE VALVE REMOTE MOUNT ANTILOCK CONTROLLER FIGURE 2B TANDEM SPREAD AXLE T
PAGE 3
DOUBLE CHECK TRAILER CONTROL EXHAUST SOLENOID BRAKE VALVE CONTROL SUPPLY SOLENOID PISTON RESERVOIR DELIVERY SUPPLY EXHAUST SERVICE BRAKE CHAMBER FIGURE 3 APPLYING: NORMAL SERVICE APPLICATION Figure 2 shows two antilock systems in which the M-12™ and M-12R™ modulator can be used. Figure 2A is a typical schematic for a full vehicle axle control system, and Figure 2B is a typical trailer installation using the M-12R ™ modulator.
PAGE 4
DOUBLE CHECK EXHAUST SOLENOID TRAILER CONTROL BRAKE VALVE CONTROL SUPPLY SOLENOID PISTON RESERVOIR DELIVERY SUPPLY EXHAUST SERVICE BRAKE CHAMBER FIGURE 4 BALANCED POSITION PREVENTIVE MAINTENANCE Important: Review the warranty policy before performing any intrusive maintenance procedures. An extended warranty may be voided if intrusive maintenance is performed during this period. 2. Inspect all air lines connected to the M-12™/M-12R™ modulator for signs of wear or physical damage.
PAGE 5
DOUBLE CHECK TRAILER CONTROL EXHAUST SOLENOID BRAKE VALVE CONTROL SUPPLY SOLENOID PISTON RESERVOIR DELIVERY SUPPLY SERVICE BRAKE CHAMBER EXHAUST FIGURE 6 ANTILOCK MODE: SOLENOIDS ACTIVATED 2. With the service brakes released, coat the exhaust port and the area around the retaining ring with a soap solution. A 1" bubble in 3 seconds is permitted. 3. If leakage is excessive around the supply and exhaust solenoids, replace the M-12™/M-12R™ modulator.
PAGE 6
DOUBLE CHECK EXHAUST SOLENOID TRAILER CONTROL BRAKE VALVE CONTROL SUPPLY SOLENOID PISTON RESERVOIR DELIVERY SUPPLY EXHAUST SERVICE BRAKE CHAMBER FIGURE 6 ANTILOCK MODE: SOLENOIDS ACTIVATED 2. Stop the engine and remove ignition key when working under or around the vehicle. When working in the engine compartment, the engine should be shut off and the ignition key should be removed.
PAGE 7
FOUR PIN CONNECTOR SHORT WIRE HARNESS BETWEEN THREE AND FOUR PIN CONNECTOR (M-12R™ MODULATOR ONLY) THREE PIN CONNECTOR TYPICAL M-12™ MODULATOR TYPICAL M-12R™ MODULATOR EXHAUST HOLD Black White WHITE BLACK COMMON SHORT WIRE HARNESS USED ON THE M-12R™ MODULATOR FIGURE 7 M-12™/M-12R™ MODULATOR CONNECTORS & WIRE HARNESS 3. Reconnect all air lines and wiring cables to the modulator or modulator/controller assembly using the identification made in MODULATOR REMOVAL, step 1. 4.
PAGE 8
CAP SCREW (4) CAP SCREW (4) ANTILOCK CONTROLLER USED ON M-12™ MODULATOR COVER PLATE USED ON THE M-12R™ MODULATOR 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 FIGURE 8 M-12™/M-12R™ MODULATOR COMPONENTS 8
PAGE 9
6. Using thumb force on the piston stem, push the piston(6) out the opposite end of the body(7). Remove o-ring(5) from the piston. 5. Depress the exhaust assembly into the bore until it exposes the groove for snap ring(14). Install snap ring(14) into its groove. Make sure it is fully seated. 7. Discard all items that have replacement parts in the maintenance kit. 6. Install o-ring(5) into its groove in piston(6). Install piston(6) into the M-12 body.
PAGE 10
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