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7

REMOVAL OF THE MC-12

 MODULATOR

ASSEMBLY

1. Remove and identify all air lines connected to the unit.

2. Disconnect the 14 pin connector from the unit by

loosening its screw and pulling the connector away from
its socket.

3. Remove and save the mounting hardware connecting

the MC-12

 modulator to the vehicle.

4. Prior to disassembly, remove as much contamination

as possible from the exterior of the assembly. Be sure
to keep the contamination away from the open ports.

INSTALLATION OF THE MC-12

MODULATOR ASSEMBLY

1. Replace the MC-12

 modulator assembly on the vehicle

using the hardware saved during removal. Connect the
air lines to the proper ports, as identified during removal.
Connect the 14 pin connector into the controller and
tighten the screw.

DISASSEMBLY

The following disassembly and assembly procedure is
presented for reference purposes and presupposes that a
major rebuild of the antilock valve is being undertaken. Several
replacement parts and maintenance kits are available which
do not require full disassembly. The instructions provided
with these parts and kits should be followed in lieu of the
instructions presented here.

CAUTION

: The MC-12

 modulator may be lightly clamped

in a bench vise during disassembly. However, over clamping
will result in damage, leakage, and/or malfunction. If a vise
is to be used, position the MC-12

 modulator so the jaws

bear on the flat area of the supply port and its opposing side
of the body.

1. Remove the EC-12

 controller (1) from the M-12

modulator by removing the controller's four mounting
bolts.

2. Lift the controller off the M-12

 modulator and detach

the wire harness from the base of the controller by
depressing the lock tab on the side of the connector
and pulling the connector from its socket in the controller.
Remove the gasket (7) from the EC-12

 controller body.

NOTE: If replacement of the controller only is required,
proceed to Step 8 of assembly.

3. Remove sealing ring (4) from the protrusion on the bottom

of the solenoid assembly.

4. Using a pair of snap ring pliers, remove retaining ring

(14). Remove the exhaust assembly (13). Remove
o-ring (12) and o-ring (11) from the l.D. and O.D.,
respectively, of the exhaust assembly.

5. Remove spring (10). Remove the inlet/exhaust assembly

(8). Remove the spring seat (9) from the inlet/exhaust
assembly.

6. Using your thumb, press the piston stem and push the

piston (6) out the opposite end of the body. Remove
o-ring (5) from the piston.

7. Discard all items that have replacement parts in the

maintenance kit.

CLEANING & INSPECTION

1. Using mineral spirits or an equivalent solvent, clean and

thoroughly dry all parts to be reused. Do not allow mineral
spirits to come into contact with the ECU connector or
solenoids.

2. Inspect the interior and exterior of all parts that will be

reused for severe corrosion, pitting and cracks. Superficial
corrosion and/or pitting on the exterior portion of the body
is acceptable.

3. Inspect the bores for deep scuffing or gouges.

4. Inspect the pipe threads in the body. Make certain they

are clean and free of thread sealant.

FIGURE 9 - EXPLODED VIEW

1

7

2

4

5

6

3

8

9

10

11

12

13

14

Summary of Contents for MC-12 MODULATOR CONTROLLER ASSY

Page 1: ...pin A and optionally pin B from the auxiliary terminal blue wire of the trailer s 7 pin connector DESCRIPTION The Bendix MC 12 modulator trailer antilock system is designed to improve vehicle stabilit...

Page 2: ...ht 14 16 14 16 14 16 10 11 N P Wheel Speed Sensor 16 18 16 18 16 18 12 13 M L Wheel Speed Sensor 16 18 16 18 16 18 Antilock Connector Pin B is an option and is used to provide constant power to the MC...

Page 3: ...s on and remains on when the trailer brakes are actuated a system problem has occurred The EC 12 controller contains a diagnostic window which FIGURE 3 SPEED SENSOR VOLTAGE CYCLE OUTPUT PEAK TO PEAK P...

Page 4: ...lock system to alter the service brake application When activated shuttles within the solenoids alter the application and exhaust of control air pressure The supply solenoidcloses preventingcontrollin...

Page 5: ...ACTIVATED EXHAUST SUPPLY EXHAUST SOLENOID CONTROL DOUBLE CHECK TRAILER CONTROL BRAKE VALVE DELIVERY PISTON SUPPLY SOLENOID SERVICE BRAKE CHAMBER DELIVERY PISTON EXHAUST SUPPLY EXHAUST SOLENOID CONTRO...

Page 6: ...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 tho...

Page 7: ...ve the EC 12 controller 1 from the M 12 modulator by removing the controller s four mounting bolts 2 Lift the controller off the M 12 modulator and detach the wire harness from the base of the control...

Page 8: ...controller onto the solenoid assembly and secure with the four 1 2 bolts and lock washers Torque to 30 60 in Ibs OPERATIONAL AND LEAKAGE TEST 1 Chock wheels Fully charge air brake system and adjust br...

Page 9: ...HE TRAILER WHILE PERFORMINGTHE INITIALSTART UPPROCEDURE and following the directions contained in the procedure Be sure to record a failure before resetting the system Reset by holding a magnet capabl...

Page 10: ...DTO TRACTOR TURNIGNITIONON APPLY TRAILERSERVICEBRAKESAND OBSERVESTATUSLAMPMOUNTED ONTRAILER NO DID STATUS LAMP ILLUMINATE GO TO SECTION I STATUS LAMP TESTING ARE STOP LAMPS ILLUMINATED YES TEST FOR PO...

Page 11: ...RDER PRESENTED AND AFTER REPLACING OR TESTING EACH COMPONENT TEST THE STATUS LAMP OPERATION 1 CHANGE TRAILER STATUS LAMP BULB 2 CHECK TRAILER STATUS LAMP WIRING GROUND 3 CHECK CONTINUITY OF WARNING WI...

Page 12: ...NO ARE ANY RED LED s ILLUMINATED YES NO YES GOTOSECTIONIV TESTINGFORPOWER TOTHEEC 12 CONTROLLER NOTE AND RECORD THE CONDITION OF ALL RED LEDS GO TO SECTION III INSPECTION FOR ILLUMINATED LEDS RED LEDs...

Page 13: ...S1 OR SNS2 LED ILLUMINATED IS RED MOD LED ILLUMINATED YES NO TESTING MOD LED IFANYOTHERREDLEDs AREILLUMINATED REPLACETHEEC 12 CONTROLLERANDREPEAT THE INITIALSTART UP PROCEDURE GO TO SECTION V TESTING...

Page 14: ...URE YES NO MAGNET HERE PERFORMAMAGNETICRESETBY PASSINGAMAGNETOVERTHE RESET INEC 12 CONTROLLER DIAGNOSTICWINDOWTHEN REMOVEMAGNET TURNIGNITIONOFF DONOTAPPLYBRAKES RECONNECTWIREHARNESSTOEC 12 CONTROLLER...

Page 15: ...RETURNED TOTHISSTEP TWICE REPLACETHE EC 12 CONTROLLER REPLACEEC 12 CONTROLLER NO GO TO SECTION III INSPECTION FOR ILLUMINATEDLEDS AND RETEST IFFAILUREPERSISTS REPLACETHEEC 12 CONTROLLER WHITE BLACK WH...

Page 16: ...N P RESISTANCE FORBENDIX WS 20 SPEEDSENSORSHOULDBEBETWEEN1500 2500 OHMS REFERTOVEHICLEMAINTENANCEMANUALIFOTHERTHANTHE WS 20 SPEEDSENSORISINUSE IFRESISTANCE NOTCORRECT DISCONNECTCONNECTORATSPEEDSENSOR...

Page 17: ...INSPEC TION FOR ILLUMINATED LED s SAME LED s ILLUMINATED NO YES RECONNECTCONNECTORATSPEED SENSORANDEC 12 CONTROLLER PASSMAGNETOVER RESET ONEC 12 CONTROLLER REMOVEMAGNETAND OBSERVELEDs IGNITIONOFFSERV...

Page 18: ...PWR LED green EC 12 Controller Power TRAILER MOUNTED STATUS LAMP POWER FROM STOPLIGHTS GROUND 7PIN TRAILER ELECTRICAL CONNECTOR CONSTANT POWER FROM TRACTOR IGNITION OPTIONAL CONNECTION GROUND A B C D...

Page 19: ...19 NOTES REFERENCES...

Page 20: ...BW1667 2004 Bendix Commercial Vehicle Systems LLC All rights reserved 4 2004 Printed in U S A...

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