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BENDIX M-30 ANTILOCK MODULATOR ASSY Manual

Antilock modulator assembly
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®
Bendix
®
M-30
™
Supply Port
(cast in 1, SUP)
Electrical Connector
FIGURE 1: M-30
Solenoid
Connector
Delivery Port
(cast in 2)
™
FIGURE 2: M-21
MODULATOR
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
AntiLock Modulator Assembly
™
MODULATOR
Supply Port
(cast in 1)
Mounting
Holes
Exhaust
(cast in 3)
M-30
(.33" diameter thru body)
Exhaust Port
(cast in 3, EXH)
Supply Port
(cast in 1)
Solenoid
Connector
Mounting
Holes
™
FIGURE 3: M-22
MODULATOR
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.
™
Modulator
Delivery Port
(cast in 2, DEL)
Mounting Holes
Exhaust
(cast in 3)
Delivery Port
(cast in 2)
1

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Summary of Contents for BENDIX M-30 ANTILOCK MODULATOR ASSY

  • Page 1 ™ FIGURE 2: M-21 MODULATOR FIGURE 3: M-22 MODULATOR DESCRIPTION braking (Figure 4). In the case of individual wheel control The Bendix ® M-30 ™ modulator replaced both the M-21 ™ applications, the modulator is always the last control valve (Figure 2) and M-22 ™...

  • Page 2: Functional Check

    FRONT AXLE SYSTEMS REAR AXLE SYSTEM WHEEL CONTROL WHEEL CONTROL AXLE WHEEL CONTROL CONTROL SERVICE BRAKE CHAMBER TO ANTILOCK ANTILOCK CONTROLLER CONTROLLER TO ANTILOCK CONTROLLER ANTILOCK ™ M-30 CONTROLLER M-30 ™ MODULATOR MODULATOR M-30 ™ MODULATOR CONTROLLER/ RELAY ASSEMBLY QUICK RELEASE VALVE M-30 ™...
  • Page 3 EXHAUST DIAPHRAGM EXHAUST VALVE EXHAUST PORT BRAKE VALVE HOLD SPRING VALVE SUPPLY OR HOLD BIAS DIAPHRAGM VALVE BRAKE CHAMBER FIGURE 5: M-30 ™ MODULATOR NON ANTILOCK APPLICATION OF SERVICE BRAKES EXHAUST DIAPHRAGM EXHAUST VALVE EXHAUST PORT BRAKE VALVE HOLD VALVE SPRING SPRING SUPPLY OR...
  • Page 4 EXHAUST DIAPHRAGM EXHAUST VALVE EXHAUST PORT BRAKE VALVE HOLD VALVE SPRING SUPPLY OR HOLD BIAS DIAPHRAGM VALVE BRAKE CHAMBER ™ FIGURE 7: M-30 MODULATOR NON ANTILOCK EXHAUST OF SERVICE BRAKES (NORMAL) valves in the modulator, the antilock controller is able to Rapid Exhaust (Figure 8) - The Rapid Exhaust operation simulate what the driver does when he pumps the brakes.
  • Page 5 EXHAUST DIAPHRAGM EXHAUST VALVE EXHAUST PORT BRAKE VALVE HOLD SPRING VALVE SUPPLY OR HOLD BIAS VALVE DIAPHRAGM BRAKE CHAMBER ™ FIGURE 8: M-30 MODULATOR NON ANTILOCK EXHAUST OF SERVICE BRAKES (RAPID) EXHAUST DIAPHRAGM EXHAUST VALVE EXHAUST PORT BRAKE VALVE HOLD VALVE SPRING SUPPLY OR...

  • Page 6: Vehicle Preparation

    EXHAUST DIAPHRAGM EXHAUST VALVE EXHAUST PORT BRAKE VALVE HOLD VALVE SPRING SUPPLY OR HOLD DIAPHRAGM BRAKE CHAMBER BIAS VALVE ™ FIGURE 10: M-30 ANTILOCK APPLICATION HELD POSITION application air to flow to the control side of the exhaust 2. Stop the engine and remove ignition key when diaphragm, which then seals the exhaust passage.

  • Page 7: Preventive Maintenance

    Do circuit. not attempt repairs requiring machining or welding 7. The leakage at the exhaust port of most Bendix compo- unless specifically stated and approved by the ™ nents, including M-30 modulators, should not exceed vehicle and component manufacturer.

  • Page 8: Electrical Control

    4. Remove the modulator from the vehicle. Mounting Hole Sizes 0.33" diameter thru body 5. Remove all air line fittings and plugs. These fittings will be re-used in the replacement modulator. BW2085 © 2004 Bendix Commercial Vehicle Systems LLC All rights reserved. 9/2004 Printed in U.S.A.

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