BENDIX M-32, M-32QR User Manual
®
Bendix® M-32™ and M-32QR™ AntiLock Modulators
SD-13-4870
M-32QR
™
Modulator*
Exhaust Port
(Casting has 3, EXH)
DESCRIPTION
Delivery Port
(Casting has
2, DEL)
Supply Port
(Casting has
Electrical
Connector
Mounting Holes
(.33" Diameter
Through Body)
1, SUP)
™
M-32
Modulator
Exhaust Port
(Casting has
3, EXH)
FIGURE 1: M-32™ AND M-32QR™ MODULATORS
Supply Port
(Casting has
1, SUP)
Electrical
Connector
* All M-32QR™ modulators
except p/n 5011281 (Bluebird)
have the shorter exhaust port.
Previous
Model
™
M-30
Modulator
FIGURE 2: M-30™ MODULATOR
The M-32™ and M-32QR™ (quick release) antilock system
modulators (Figure 1) are high capacity, on/off air valves
that incorporate 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 .
The M-32QR™ modulator is the direct replacement for the
M-30™ (Figure 2) modulator in all applications. The M-32QR
modulator includes a bias valve to provide an internal quick
release function. In applications using an M-32™ modulator,
an external quick release valve may be required, depending
on the system design (see Figure 3 for typical system
schematics). 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. 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.
™
The supply, delivery and exhaust ports on the M-32
modulator are identified with a cast, embossed numeral for
positive identification.
Identification Air Line Connection
1, SUP Supply
(incoming air from foot, relay or quick release valve)
2, DEL Delivery
(air delivery to service actuators)
3, EX H Exhaust
™
1
Front Axle Systems
Rear Axle System
Wheel Control
Service Brake
Service Brake
Chamber
Chamber
To Antilock
Controller
M-32QR
Modulator
M-32QR
Modulator
To Antilock
Controller
™
™
or
Service Brake
Chamber
To Antilock
Controller
™
M-32
or M-32QR
Modulator
Quick Release Valve
M-32™ or M-32QR
Modulator
™
™
To Antilock
Controller
Service Brake
or
Chamber
Axle ControlWheel Control
To Antilock
Controller
Quick
Release
Valve
M-32™ or
M-32QR
Modulator
Wheel Control
To Antilock
Controller
M-32™ or M-32QR
Modulator
Controller/Relay
Assembly
™
To Antilock
Controller
Service &
Spring Brake
Chamber
M-32
FIGURE 3: TYPICAL WHEEL AND AXLE CONTROL SYSTEMS
NOTE: use of a quick release valve is not typically required with the M-32QR™ modulator. Refer to vehicle specifications for recommended configuration.
™
or M-32QR
Modulator
™
™
FUNCTIONAL CHECK
A wiring harness connects the vehicle modulators to the
controller. The ABS controller is able to simultaneously and
independently control the individual modulators. When vehicle
power is supplied to the ABS ECU, a modulator "chuf f" test
is performed. When the brake pedal is depressed and the
ignition turned on, the modulator "chuff" test can be heard.
This test will verify if the modulator is functioning
pneumatically correct. The modulators will exhaust air in
the sequence of right front, left front, right rear , left rear. If
they do not follow this sequence, proceed with modulator
troubleshooting.
OPERATION
NON-ANTILOCK BRAKE APPLICATION (Figure 4)
During normal, non antilock braking, both solenoids are deenergized (no electrical power). Brake application air enters
the Supply port of the modulator and flows to the exhaust
diaphragm. Air pressure, along with spring force, seat s the
exhaust diaphragm on the exhaust passage, thus preventing
the escape of service air. Simultaneously, application air
flows to the supply diaphragm and forces it away from its
seat. Air flows past the open supply port and out the
modulator delivery port to the service brake chambers.
NON-ANTILOCK HOLD (Figure 5)
When the desired air pressure is attained in the service
brake chambers, the brake system is in the Holding position.
In the Holding position, both solenoids in the modulator
remain de-energized and the balance of the internal
components remain in the same position as they assumed
during application.
NON-ANTILOCK EXHAUST
The manner in which air exhausts through the modulator
differs depends upon how rapidly the brake application is
released by the driver.
Normal Exhaust (Figure 6) - During a normal, relatively
“slow” brake release, air moves back through the modulator
in the reverse direction as it flowed during application. The
internal components of the modulator will remain in the same
position as they assumed during application until air pressure
decreases to approximately one half psi, at which time the
supply diaphragm will seat on the supply passage. A
relatively small amount of air will generally be expelled from
the modulator exhaust port during “slow” brake release.
2
Brake
Valve
Supply
Port
Delivery
Port
Brake
Valve
Supply
Port
Bias
Valve
Delivery
Port
Brake
Chamber
Supply or Hold
Diaphragm
Spring
Exhaust
Port
FIGURE 4: M-32™ AND M-32QR™ MODULATORS NON-ANTILOCK APPLICATION OF SERVICE BRAKES
Brake
Valve
Supply or Hold
Diaphragm
Supply
Port
Exhaust
Diaphragm
Delivery
Port
Exhaust
Valve
™
M-32
Modulator
Brake
Chamber
Supply or Hold
Diaphragm
Brake
Valve
Supply or Hold
Diaphragm
Spring
Exhaust
Port
Supply
Port
Exhaust
Diaphragm
Bias
Valve
Exhaust
Valve
M-32QR
Modulator
Delivery
Port
Brake
Chamber
™
Brake
Chamber
Spring
FIGURE 5: M-32
Brake
Valve
Supply or Hold
Diaphragm
Spring
Exhaust
Valve
™
M-32
Exhaust
Port
™
AND M-32QR™ MODULATORS NON-ANTILOCK BRAKE APPLICATION HELD POSITION
Supply
Port
Exhaust
Port
Exhaust
Diaphragm
Delivery
Port
Exhaust
Diaphragm
Modulator
Brake
Chamber
Exhaust
Valve
™
M-32
Modulator
Brake
Valve
Supply or Hold
Diaphragm
Spring
Spring
Exhaust
Port
Supply
Port
Exhaust
Port
Exhaust
Diaphragm
Bias
Valve
Exhaust
Diaphragm
Exhaust
Valve
M-32QR
Modulator
Delivery
Port
Exhaust
Valve
M-32QR
Modulator
™
Brake
Chamber
™
FIGURE 6: M-32™ and M-32QR™ MODULATORS “SLOW” NON-ANTILOCK EXHAUST OF SERVICE BRAKES
3
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