BENDIX M32 M32QR ANTILOCK MODULATOR ASSY User manual

1
Supply Port
(Casting has
1,SUP)
Exhaust Port
(Casting has
3,EXH)
Supply Port
(Casting has
1,SUP)
Exhaust Port
(Casting has 3, EXH)
Electrical
Connector
MountingHoles
(.33"Diameter
ThroughBody)
Electrical
Connector
DeliveryPort
(Casting has
2,DEL)
M-32™
Modulator
M-32QR™
Modulator*
®
SD-13-4870
DESCRIPTION
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.
Thesolenoidsprovidetheelectro-pneumaticinterfacebetween
theantilockcontrollerelectronicsandtheairbrakesystem.
The modulator is used to control the braking function on
individualordualserviceactuatorsduringantilockactivity.
The M-32QR™modulator is the direct replacement for the
M-30™(Figure2)modulatorinallapplications.TheM-32QR™
modulatorincludesabiasvalvetoprovidean internal quick
releasefunction. Inapplicationsusing anM-32™modulator,
anexternalquickrelease valvemayberequired,depending
on the system design (see Figure 3 for typical system
schematics). Whenusedtocontrolbothservicechambers
on an axle or two chambers on the same side of a tandem
axle,themodulatoris sometimes mountedaheadofaquick
release valve, which provides quick exhaust of service
applicationsduringnormalbraking. In thecaseofindividual
wheelcontrolapplications,themodulatorisalwaysthelast
control valve through which air passes on its way to the
servicebrakeactuator.
Bendix®M-32™and M-32QR™AntiLock Modulators
FIGURE 1: M-32™AND M-32QR™MODULATORS
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
fromtheantilockcontrollertothemodulator. Twomounting
holesare provided for frame orcross member mounting of
thevalve.
The supply, delivery and exhaust ports on the M-32™
modulatorareidentifiedwithacast,embossednumeralfor
positiveidentification.
Identification Air Line Connection
1, SUP Supply
(incomingairfromfoot,relayorquickreleasevalve)
2, DEL Delivery
(airdeliverytoserviceactuators)
3,EXH Exhaust
Previous
Model
M-30™
Modulator
FIGURE 2: M-30™MODULATOR
* All M-32QR™modulators
exceptp/n5011281(Bluebird)
havetheshorterexhaustport.

2
Service &
Spring Brake
Chamber
ToAntilock
Controller
Controller/Relay
Assembly
M-32™or M-32QR™
Modulator
M-32™or M-32QR™
Modulator
To Antilock
Controller
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.
NON-ANTILOCK HOLD (Figure 5)
When the desired air pressure is attained in the service
brakechambers,the brakesystemisintheHoldingposition.
In the Holding position, both solenoids in the modulator
remain de-energized and the balance of the internal
componentsremainin the same position as they assumed
duringapplication.
NON-ANTILOCK EXHAUST
The manner in which air exhausts through the modulator
differs depends upon how rapidly the brake application is
releasedbythedriver.
Normal Exhaust (Figure 6) - During a normal, relatively
“slow”brakerelease,air moves backthroughthemodulator
in the reverse direction as it flowed during application. The
internalcomponentsofthemodulatorwillremaininthesame
positionastheyassumedduringapplicationuntilairpressure
decreases to approximately one half psi, at which time the
supply diaphragm will seat on the supply passage. A
relativelysmallamountofair will generally beexpelledfrom
themodulatorexhaustportduring“slow”brakerelease.
RearAxleSystem
FUNCTIONAL CHECK
A wiring harness connects the vehicle modulators to the
controller.TheABS controller is able to simultaneouslyand
independentlycontroltheindividualmodulators.Whenvehicle
powerissuppliedtotheABSECU,amodulator"chuff"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)
Duringnormal,nonantilockbraking,both solenoids are de-
energized(noelectrical power). Brakeapplicationairenters
the Supply port of the modulator and flows to the exhaust
diaphragm. Airpressure,alongwithspringforce,seatsthe
exhaustdiaphragmontheexhaustpassage,thuspreventing
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
modulatordeliveryporttotheservicebrakechambers.
FrontAxleSystems
Axle ControlWheel Control Wheel Control
Service Brake
Chamber
M-32™or M-32QR™
Modulator
M-32™or M-32QR™
Modulator
Quick Release Valve M-32™or
M-32QR™
Modulator
Service Brake
Chamber
Quick
Release
Valve
To Antilock
Controller
To Antilock
Controller
To Antilock
Controller
or
Service Brake
Chamber
M-32QR™
Modulator
To Antilock
Controller
M-32QR™
Modulator
Service Brake
Chamber
Wheel Control
or
To Antilock
Controller

3
FIGURE 4: M-32™AND M-32QR™MODULATORS NON-ANTILOCK APPLICATION OF SERVICE BRAKES
FIGURE 5: M-32™AND M-32QR™MODULATORS NON-ANTILOCK BRAKE APPLICATION HELD POSITION
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
M-32™
Modulator M-32QR™
Modulator
Bias
Valve
Delivery
Port
Supply
Port
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
Delivery
Port
Supply
Port
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
M-32™
Modulator M-32QR™
Modulator
Bias
Valve
Delivery
Port
Supply
Port
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
Delivery
Port
Supply
Port
FIGURE 6: M-32™and M-32QR™MODULATORS “SLOW” NON-ANTILOCK EXHAUST OF SERVICE BRAKES
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
M-32™
Modulator M-32QR™
Modulator
Bias
Valve
Delivery
Port
Supply
Port
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
Delivery
Port
Supply
Port

4
Rapid Exhaust (Figure 7) - The Rapid Exhaust operation
describedinthefollowing text occurswhenthemodulatoris
controllingservicechamber(s). Duringarapidbrake release
the quick release modulator will exhaust air differently to a
“slow”brake release.
An example of this would be the case if the driver made a
severe brake application then lifted his foot from the foot
valve.Duringarapidbrakerelease,theairpreviouslydelivered
to the brake chamber is vented through the M-32™
modulatorsasfollows:
For the M-32QR™Modulator: Thebiasvalve moves to its
closed position, closing the air return route to the brake
valve’sexhaust. Airpressureagainsttheexhaustvalvewithin
theM-32™modulatorovercomesthespringforce andallows
airtoexhaustthroughtheM-32QR™modulator exhaustport.
Residualairpressurebetweenthe bias valve andthebrake
pedalflows back to the brake valve exhaust.
For the M-32™Modulator: As in the “slow” brake release,
air pressure travels back to the brake valve’s exhaust, but
also the air pressure against the exhaust valve within the
M-32™modulatorovercomesthespring forceandallowsair
toexhaust through the M-32™modulator exhaustport.
ANTILOCK OPERATION
GENERAL
Ifaservicebrakeapplicationismadeandtheantilocksystem
detects an impending wheel lockup, the antilock controller
willmakea controlledbrakeapplicationusingthemodulator.
Inordertocontrolthebrakeapplication,thecoilsofthetwo
solenoidvalvescontainedin themodulatorareenergizedor
de-energizedinapreprogrammedsequencebytheantilock
controller. Whena solenoidcoilisenergized,anddepending
whethertheexhaust or hold solenoid is energized, it either
opens or closes, thereby causing the exhaust or
reapplication of air pressure to the brake actuator. The
solenoidsinthemodulatorarecontrolledindependentlyby
theantilockcontroller(ECU).
An experienced driver (of a vehicle without ABS) who
encounterswheellock-upmaysometimes“pumpthebrakes”
in order to attempt to prevent wheel lock-up and maintain
vehicle control. In the case of anABS braking system, the
driverdoesnotneed to“pumpthebrakes”since theantilock
controller is able to apply and release the brakes using the
modulators,withfargreaterspeedandaccuracy. Depending
onthenumberofmodulatorsused,somesystemsareable
toapplybraking power to wheels independently (see page
2).
ANTILOCK EXHAUST (Figure 8)
When wheel lock is detected or imminent, the antilock
controller energizes the supply and exhaust solenoids in
themodulator.
Energizingthesupplysolenoidallowsapplication air toflow
to the control side of the supply diaphragm. Air pressure
actingonthesupply diaphragm, alongwiththespringforce,
enables the diaphragm to prevent further delivery of air to
thebrakechamber.
Energizing the exhaust solenoid shuts off the air normally
appliedtothecontrol side oftheexhaustdiaphragmto keep
it closed. Air pressure acting on the exhaust diaphragm,
overcomesthespringforce,andallowsairtoexhaustthrough
the exhaust port.
ANTILOCK HOLD MODE (Figure 9)
The antilock controller will place the modulator in the Hold
positionwhenitsensesthatthecorrectwheelspeed(braking
force) has been attained. The antilock controller will also
FIGURE 7: M-32™AND M-32QR™MODULATORS RAPID NON-ANTILOCK EXHAUST OF SERVICE BRAKES
Supplyor Hold
Diaphragm
Open
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Open
Exhaust
Port
M-32™
Modulator M-32QR™
Modulator
Bias
Valve
Delivery
Port
Supply
Port
Supplyor Hold
Diaphragm
Open
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Open
Exhaust
Port
Delivery
Port
Supply
Port

5
FIGURE 8: M-32™MODULATOR ANTILOCK EXHAUST OF BRAKES
Supplyor Hold
Diaphragm
Closed
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Open
Exhaust
Port
M-32™
Modulator M-32QR™ Modulator
Bias
Valve
Delivery
Port
Supply
Port
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
Delivery
Port
Supply
Port
FIGURE 9: M-32™AND M-32QR™MODULATORS ANTILOCK APPLICATION HELD POSITION
Supplyor Hold
Diaphragm
Closed
Spring
Brake
Chamber
Brake
Valve
Exhaust
Valve
Closed
Exhaust
Port
M-32™
Modulator M-32QR™
Modulator
Bias
Valve
Delivery
Port
Supply
Port
Supplyor Hold
Diaphragm
Spring
Brake
Chamber
Brake
Valve
Exhaust
Diaphragm
Exhaust
Valve
Exhaust
Port
Delivery
Port
Supply
Port
place the modulator in the hold position, prior to entering
the reapply mode, when it detects recovery from a locked
wheel condition. In this mode of operation, the modulator
supply/hold solenoid remains energized while the exhaust
solenoidreturnstoitsnormalposition. Theexhaustsolenoid
allowsapplicationairtoflowtothecontrolsideoftheexhaust
diaphragm, which then seals the exhaust passage. With
the exhaust diaphragm seated, further exhaust of brake
chamber air pressure is prevented. Because the supply
solenoidremainsenergized,the supply diaphragmremains
seated, thus preventing application air from flowing to the
delivery port and out to the brake chamber. The modulator
can enter both the antilock exhaust or reapply mode from
the antilock hold mode depending on the needs of the
antilockcontroller.
ANTILOCK “REAPPLY” MODE
If the antilock controller senses that wheel speed has
increasedsufficientlyenoughtoallowre-applicationofbraking
pressure,withoutfurtherwheellock-up,itde-energizesthe
supply solenoid. With both solenoids de-energized, the
modulatorre-appliesairtothe brakesinthesamemannerit
didduringanon-antilockevent.
Solenoid
Energized:
Moves to
Down
Position
Solenoid
Energized:
Moves to
Down
Position
Solenoid
Energized:
Moves to
DownPosition
Solenoid
Energized:
Moves to
Down
Position
Exhaust
Diaphragm
Solenoid
Energized:
Moves to
DownPosition
Solenoid
Energized:
Moves to
Down
Position
Solenoid
Returns
toUp
Position
Solenoid
Returns
toUp
Position

6
PREVENTIVE MAINTENANCE
GENERAL
Perform the tests and inspections presented at the
prescribed intervals. If the modulator fails to function as
described, or leakage is excessive, it should be replaced
with a new Bendix unit, available at any authorized parts
outlet.
EVERY MONTH, 10,000 MILES OR 350
OPERATING HOURS
1. Remove any accumulated contaminates and visually
inspecttheexteriorfor excessivecorrosionandphysical
damage.
2. Inspect all air lines and wire harnesses connected to
the modulator for signs of wear or physical damage.
Replaceas necessary.
3. Testairlinefittingsfor leakage and tighten orreplaceas
necessary.
4. Perform the ROUTINE OPERATION AND LEAKAGE
TESTINGdescribedinthismanual.
OPERATION & LEAKAGE TESTS
LEAKAGE TEST
1. Park the vehicle on a level surface and block or chock
the wheels. Release the parking brakes and build the
air system to full pressure.
2. TurntheengineOFFandmake4or5brakeapplications
and note that the service brakes apply and release
promptly.
3. Build system pressure to governor cut-out and turn the
engineOFF.
4. After determining the pressure loss with the brakes
released (2 PSI/minute allowed), make and hold a full
servicebrakeapplication. Allow thepressuretostabilize
foroneminute.
5. Begintimingpressurelossfor twominuteswhilewatch-
ingthe dash gauges for apressure drop. The leakage
ratefortheservicereservoirsshouldnotexceed3 PSI/
minute.
6. If either circuit exceeds the recommended two PSI/
minute, apply soap solution to the exhaust port of the
modulatorandanyothercomponentsintherespective
circuit.
7. Theleakageatthe exhaust portofmostBendixcompo-
nents,includingM-32™modulators,shouldnotexceed
a one-inch bubble in three seconds. If leakage at the
modulator is determined to exceed the maximum
limits, replace the modulator.
OPERATION TEST
Toproperlytestthefunctionof themodulatorwillrequiretwo
(2)servicetechnicians.
1. Park the vehicle on a level surface and block or chock
the wheels. Release the parking brakes and build the
air system to governor cut out.
2. Turn the engine ignition key to the OFF position then
makeand hold a full brake application.
3. With the brake application held and one (1) service
technicianpostedatone (1) of the modulators, turn the
vehicle ignition key to the ON position. ONE OR TWO
SHORT bursts of air pressure should be noted at the
modulatorexhaust.Repeatthetest for each modulator
onthevehicle.Ifatleasta single burst of exhaust is not
noted or the exhaust of air is prolonged and not short,
sharpandwell defined, perform the ElectricalTests.
ELECTRICALTESTS
1. Before testing the solenoid assembly of a suspect
modulator,itslocationonthevehicleshouldbeconfirmed
usingtheTroubleShooting orStartUp procedureforthe
specificantilockcontrollerinuse. (See theServiceData
Sheetfortheantilockcontroller for this procedure.)
2. Proceed to the modulator in question and inspect its
wiringconnector.Disconnect the connectorandtestthe
resistance between the pins ON THE MODULATOR.
RefertoFigures10and11.
A. HOLDTOSOURCE(41-42):Read4.9to5.5Ohms.
B. EXHAUSTTOSOURCE(43-41):Read4.9to5.5Ohms.
C. EXHAUSTTO HOLD(43-42):Read9.8to11.0 Ohms.
D. Individually test the resistance of each pin to vehicle
groundandnotethere isNOCONTINUITY.
Iftheresistancereadingsareasshown,thewireharness
leading to the modulator may require repair or
replacement. Before attempting repair or replacement
ofthewireharness,refertothetestprocedures specified
fortheantilockcontrollerinuseforpossiblefurthertesting
that may be required to substantiate the wire harness
problem.IftheresistancevaluesareNOTASSTATED,
replacethemodulator.
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURYOR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.

7
Twist-LockConnector
(BayonetConnector)
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. Where circumstances require that the
enginebein operation, EXTREMECAUTIONshould
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Useonlytheproper tools and observe
all precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems,makecertain todrainthe airpressurefrom
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS™
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.
5. Following the vehicle manufacturer’s
recommendedprocedures,deactivate the electrical
system in a manner that safely removes all
electrical power from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.
8. Use only genuine Bendix®replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
11. Forvehicles with AntilockTractionControl (ATC),
the ATC function must be disabled (ATC indicator
lampshouldbeON)priortoperforminganyvehicle
maintenance where one or more wheels on a
drive axle are lifted off the ground and moving.
MODULATOR REMOVAL
1. Locate the modulator that will be replaced and clean
theexterior.
2. Identify and mark or label all air lines and their respec-
tive connections on the valve to facilitate ease of
installation.
3. Disconnect both air lines and the electrical connector.
4. Removethemodulatorfromthe vehicle.
5. Remove all air line fittings and plugs. These fittings
will be re-used in the replacement modulator.
FIGURE 10: M-32™AND M-32QR™MODULATORS CONNECTOR VIEWS
Source 41
Hold 42
Exhaust 43
42
41
43
Threaded
(Metric)
Connector
42
41
43
42
41
43

8
FIGURE 11: M-32™AND M-32QR™MODULATORS DIN SYMBOL
BW2335 © 2004 Bendix Commercial Vehicle Systems LLC 5/2004 Printed in U.S.A. All rights reserved.
Port Designation
Supply 1
Delivery 2
Exhaust 3
Electrical Control
Source 41
Hold 42
Exhaust 43
MODULATOR INSTALLATION
1. Installallairlinefittingsandplugs,makingcertainthread
sealingmaterialdoesnotenterthevalve.
2. Installtheassembledvalveonthevehicle.
3. Reconnect both air lines to the valve using the identifi-
cation made during VALVE REMOVALstep 5.
4. Reconnecttheelectricalconnectorto the modulator.
5. Afterinstallingthevalve, test allairfittingsforexcessive
leakageandtightenasneeded.
TECHNICAL INFORMATION
Porting 1 Supply Port (from brake, relay or quick
releasevalve)-1/2" NPT
1 DeliveryPort(brakeactuator)-1/2"NPT
Optional: 1 Push-to-connectfor 1/2" tubing
2 NPTsupply,PTCdelivery
Solenoid Voltage: 12VoltsDCNominal,optional
24Voltavailable.
Weight: 1.7pounds
Maximum Operating Pressure: 150 psi Gauge
Operating Temperature Range: -40 to 185
degrees
Fahrenheit
Pressure Differential: 1psimaximum(supplytodelivery)
Mounting Hole Sizes: 0.33" diameter through body