BENDIX BW1667 User's Manual
Contents
1. 12 controller senses wheel lockup it will command the antilock system to alter the service brake application When activated shuttles within the solenoids alter the application and exhaust of control air pressure The supply solenoid closes preventing control line pressure from entering the modulator Then the exhaust solenoid opens allowing control pressure to exhaust from the top side of the piston through the exhaust port of the solenoid assembly This activity occurs in a pulsating manner simulating pumping of the brakes PREVENTIVE MAINTENANCE 1 Every 3 months 25 000 miles or 900 operating hours perform SERVICE CHECKS 2 Every twelve months 100 000 miles or 3600 operating hours disassemble the relay valve portion of the M 12 Modulator and clean parts with mineral spirits DO NOT DISASSEMBLE THE SOLENOID ASSEMBLY Replace all rubber parts and any parts worn or damaged Check for proper operation before placing vehicle in service FIGURE 5 BALANCED POSITION NORMAL SERVICE APPLICATION TRAILER CONTROL DOUBLE CHECK BRAKE VALVE CONTROL PISTON DELIVERY EXHAUST SUPPLY EXHAUST SOLENOID SUPPLY SOLENOID SERVICE BRAKE CHAMBER 5 FIGURE 6 EXHAUSTING NORMAL SERVICE APPLICATION FIGURE 7 ANTILOCK MODE SOLENOIDS ACTIVATED EXHAUST SUPPLY EXHAUST SOLENOID CONTROL DOUBLE CHECK TRAILER CONTROL BRAKE VALVE DELIVERY PISTON SUPPLY SOLENOID SERVICE BRAKE2. CONTROLLER CONNECTOR EC 12 CONTROLLER DIAGNOSTIC WINDOW 19 NOTES amp REFERENCES BW1667 2004 Bendix Commercial Vehicle Systems LLC All rights reserved 4 2004 Printed in U S A
3. FUNCTIONING NORMALLY MAKE NOTES OF THE PARTS REPLACED OR REPAIRED AND STEPS TAKEN AMBER STATUS LAMP BLINKS ONCE THEN GOES OUT SYSTEM OK WITH TRAILER CONNECTED TO TRACTOR TURN IGNITION ON APPLY TRAILER SERVICE BRAKES AND OBSERVE STATUS LAMP MOUNTED ON TRAILER NO DID STATUS LAMP ILLUMINATE GO TO SECTION I STATUS LAMP TESTING ARE STOP LAMPS ILLUMINATED YES TEST FOR POWER TO THE TRAILER AT 7 PIN CONNECTOR NO YES GO TO SECTION II INSPECTION FOR ILLUMINATED LEDS Troubleshooting INITIAL START UP PROCEDURE TYPICAL LOCATIONS FOR AMBER STATUS LAMP TYPICAL 7 PIN TRAILER ELECTRICAL CONNECTOR 7 PIN TRAILER CONNECTOR CONSTANT POWER IGNITION STOPLIGHT POWER GROUND 11 Troubleshooting SECTION I TRAILER STATUS LAMP TESTING REPEAT THE INITIAL START UP PROCEDURE START HERE USING A JUMPER WIRE CONNECT PIN A TO D THEN B TO D WITH THE CONNECTION IN PLACE NOTE THE CONDITION OF TRAILER STATUS LAMP TRAILER STATUS LAMP ON NO YES REPLACE EC 12 CONTROLLER AND RETEST CHECK THE FOLLOWING IN THE ORDER 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 WIRE BETWEEN PIN D ON THE 14 PIN CONNECTOR AND THE TRAILER STATUS LAMP SOCKET EC 12 CONTROLLER WIRE HARNESS CONNECTOR WITH TRACTOR IGNITION OFF DI
4. 1 SD 13 4762 Bendix MC 12 Modulator Controller Assembly FIGURE 1 MC 12 MODULATOR CONTROLLER ASSY wheel end send wheel speed information to the EC 12 controller through the 14 pin connector The sensors are actually AC generators They house magnets which create a magnetic field When the field is interrupted by an irregular surface such as a tone ring AC voltage is produced The frequency of voltage increases or decreases as wheel speed increases or decreases During normal non antilock operation the M 12 modulator s inlet solenoid is open and the exhaust solenoid is closed In this condition the M 12 modulator functions as a regular R 12 relay valve It receives a control signal from the foot valve which passes through the open inlet solenoid and causes the brakes to apply in proportion to the amount of control pressure If wheel lock up is impending the EC 12 controller commands the solenoids to modulate brake chamber pressure on the axle s in which the system is installed The MC 12 modulator controller receives its power from the vehicle s stop light circuit pin 4 on the standard seven pin connector red The power enters the EC 12 controller at 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 stability by reducing wheel l
5. AND BEGIN TESTING ANY RED LED s ON NO TURN IGNITION ON amp APPLY amp HOLD BRAKES ON PASS MAGNET OVER RESET ON EC 12 CONTROLLER REMOVE MAGNET AND OBSERVE THE LEDs RECONNECT EC 12 CONTROLLER CONNECTOR TURN IGNITION ON amp APPLY amp HOLD BRAKES ON PASS MAGNET OVER RESET ON EC 12 CONTROLLER REMOVE MAGNET AND OBSERVE LEDs YES A B C D E F G H J K L M N P M SNS 2 L SNS 2 N SNS 1 P SNS 1 TESTING SPEED SENSOR RESISTANCE MAGNET HERE RESETTING EC 12 CONTROLLER MAGNET HERE RESETTING EC 12 CONTROLLER EC 12 CONTROLLER WIRE HARNESS CONNECTOR TURN IGNITION OFF DO NOT APPLY BRAKES AND CHECK FOLLOWING A REMOVE CONNECTOR FROM EC 12 CONTROLLER AND MEASURE RESISTANCE BETWEEN SPEED SENSOR M amp L AND N amp P RESISTANCE FOR BENDIX WS 20 SPEED SENSOR SHOULD BE BETWEEN 1500 2500 OHMS REFER TO VEHICLE MAINTENANCE MANUAL IF OTHER THAN THE WS 20 SPEED SENSOR IS IN USE IF RESISTANCE NOT CORRECT DISCONNECT CONNECTOR AT SPEED SENSOR INSPECT CONNECTOR THEN CHECK RESISTANCE BETWEEN PINS ON SENSOR IF RESISTANCE IS NOT CORRECT BETWEEN 1500 2500 OHMS FOR THE BENDIX WS 20 SPEED SENSOR REPLACE SENSOR OTHERWISE PROCEED TO STEP B B CHECK GAP BETWEEN SPEED SENSOR AND EXCITER OR TONE RING GAP FOR BENDIX WS 20 SPEED SENSOR SPEED SENDER IS BETWEEN 0 015 INCHES IF SENSOR GAP MUST BE ADJUSTED CHECK FOR LOOSE OR WORN WHEEL BEARINGS BEFORE RE GAPPING SEN
6. APPLYING Normal Service Application When a normal service brake application is made and the EC 12 controller does not sense impending wheel lock up control air pressure from the brake valve enters the modulator control port The air passes through the supply solenoid and acts on the modulator s piston The piston closes the modulator exhaust and opens the inlet delivering supply air out the delivery ports FIGURE 4 APPLYING NORMAL SERVICE APPLICATION DELIVERY PISTON EXHAUST SUPPLY EXHAUST SOLENOID CONTROL DOUBLE CHECK TRAILER CONTROL BRAKE VALVE SUPPLY SOLENOID SERVICE BRAKE CHAMBER 4 BALANCED POSITION Normal Service Application The modulator reaches a balanced position when control pressure acting upon the top side of the piston approaches that of the air acting upon the underside of the piston The piston moves upward and closes the inlet valve while the exhaust remains closed This prevents the modulator from delivering or exhausting air EXHAUSTING Normal Service Application When the brake valve is released control pressure exhausts through the supply solenoid and the check valve in the solenoid housing and out the exhaust port of the brake valve As the piston moves upward the modulator s exhaust opens allowing air from the piston s underside to exhaust through the modulator exhaust port ANTILOCK MODE Solenoids Activated If a service brake application is made and the EC
7. C 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 amp 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 8 5 Inspect all air line fittings and plugs for corrosion C
8. CHAMBER DELIVERY PISTON EXHAUST SUPPLY EXHAUST SOLENOID CONTROL DOUBLE CHECK BRAKE VALVE SUPPLY SOLENOID SERVICE BRAKE CHAMBER TRAILER CONTROL 6 SERVICE CHECKS Ensure that all wiring and connectors are secure and free from visible damage Although the MC 12 modulator assembly contains self check diagnostics the LED Light Emitting Diode display should be inspected to ensure that the LEDs are functional With the trailer brakes actuated a magnet 800 gauss capable of picking up 3 ounces held to the LED reset area should cause all of the LEDs to illuminate If one or more of the LEDs DO NOT ILLUMINATE and the optional status light indicates proper system function the non illuminated LED s should be noted for future reference Although the diagnostic capabilities will be limited the system will continue to function as designed The MC 12 modulator assembly monitors the electronics of the system upon initial trailer brake application However the vehicle should be road tested periodically to verify proper solenoid function The solenoids can be tested by making an aggressive trailer stop from a speed of 20 m p h When an antilock stop is made solenoid pulsation creates an audible burst of air which can be heard from the outside of the trailer WARNING PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH When working on or around a vehicle the following gen
9. OUND C EC 12 CONTROLLER WIRE HARNESS CONNECTOR 15 Troubleshooting SECTION V TESTING THE MODULATOR SAME RED LED s ILLUMINATED NO YES YES ARE ANY RED LED s ILLUMINATED INSPECT CONNECTOR AND RECONNECT TO EC 12 CONTROLLER TURN IGNITION ON amp APPLY amp HOLD BRAKES ON PASS MAGNET OVER RESET ON EC 12 CONTROLLER REMOVE MAGNET AND NOTE REACTION OF RED LEDS ARE RESISTANCE VALUES CORRECT YES REPEAT INITIAL START UP PROCEDURE IF TESTING HAS RETURNED TO THIS STEP TWICE REPLACE THE EC 12 CONTROLLER REPLACE EC 12 CONTROLLER NO GO TO SECTION III INSPECTION FOR ILLUMINATED LEDS AND RETEST IF FAILURE PERSISTS REPLACE THE EC 12 CONTROLLER WHITE BLACK WHITE BLACK M 12 MODULATOR 4 PIN CONNECTOR START HERE MAGNET HERE RESETTING EC 12 CONTROLLER REPLACE M 12 MODULATOR NO TURN IGNITION OFF AND DO NOT APPLY BRAKES SEPARATE EC 12 CONTROLLER FROM THE M 12 MODULATOR DISCONNECT 4 PIN CONNECTOR BETWEEN M 12 MODULATOR amp EC 12 CONTROLLER AND TEST RESISTANCE ON THE MODULATOR CONNECTOR BLACK to BLACK READ 9 to 12 OHMS WHITE to WHITE READ 9 to 12 OHMS 16 Troubleshooting SECTION VI PART A TESTING THE WHEEL SPEED SENSOR START HERE REPEAT THE INITIAL START UP PROCEDURE ARE ANY RED LEDs ILLUMINATED GO TO SECTION III INSPECTION FOR ILLUMINATED LEDs NO YES GO TO SECTION VI PART B
10. SCONNECT 14 PIN WIRE HARNESS CONNECTOR FROM EC 12 CONTROLLER THEN TURN TRACTOR IGNITION ON AND MAKE AND HOLD A BRAKE APPLICATION A B C D E F G H J K L M N P POWER A amp B TRAILER STATUS LAMP D 12 Troubleshooting SECTION II INSPECTION FOR ILLUMINATED LED s YES YES GO TO SECTION IV TESTING FOR POWER TO THE EC 12 CONTROLLER NO NO START HERE IS GREEN PWR LED ILLUMINATED REPLACE THE EC 12 CONTROLLER ARE ANY RED LED s ILLUMINATED NO ARE ANY RED LED s ILLUMINATED YES NO YES GO TO SECTION IV TESTING FOR POWER TO THE EC 12 CONTROLLER NOTE AND RECORD THE CONDITION OF ALL RED LEDS GO TO SECTION III INSPECTION FOR ILLUMINATED LEDS RED LEDs ANY ILLUMINATED CHECKING PWR LED WITH TRACTOR IGNITION ON AND BRAKES HELD APPLIED INSPECT EC 12 CONTROLLER FOR PRESENCE OF ILLUMINATED LEDS AND RECORD GO TO SECTION I TRAILER STATUS LAMP TESTING ON CHECKING VOLT LED ON IS RED VOLT LED ON 13 Troubleshooting SECTION III INSPECTION FOR ILLUMINATED LEDS NOTE RED CONT LED IN EC 12 CONTROLLER DIAGNOSTICS WINDOW START HERE NO ON INSPECTING CONT LED NO IS EITHER OR BOTH RED SNS1 OR SNS2 LED ILLUMINATED IS RED MOD LED ILLUMINATED YES NO TESTING MOD LED IF ANY OTHER RED LEDs ARE ILLUMINATED REPLACE THE EC 12 CONTROLLER AND REPEAT THE INITIAL STAR
11. SOR REFER TO VEHICLE MAINTENANCE MANUAL FOR WORN BEARINGS C IF SENSOR GAP IS CORRECT CHECK WHEEL BEARING FOR FREE PLAY TO VERIFY IT COMPLIES TO MANUFACTURER S RECOMMENDATIONS D MAKE CERTAIN EXCITER OR TONE RING IS IN PLACE AND INSPECT CONDITION CHECK FOR MISSING OR DAMAGED TEETH AND THAT IT RUNS TRUE AND PERPENDICULAR TO SENSOR FACE E CHECK WIRING HARNESS AND CONNECTORS THAT RUN TO SENSOR F CHECK FOR DRAGGING BRAKES OVER ADJUSTED TRAPPED AIR IN ACTUATOR OUT OF ROUND DRUMS FAULTY RETURN SPRINGS PARKING BRAKE SYSTEM FAULTS ETC AND CORRECT AND RETEST 17 Troubleshooting SECTION VI PART B TESTING THE WHEEL SPEED SENSOR REPEAT THE INITIAL START UP PROCEDURE REPLACE THE EC 12 CONTROLLER YES ARE ANY LED s ILLUMINATED YES ARE SAME RED LEDS ILLUMINATED YES CORRECT RESISTANCE NO DISCONNECT CONNECTOR AT SPEED SENSOR INSPECT THE CONNECTOR THEN CHECK THE RESISTANCE BETWEEN TWO PINS ON SENSOR RESISTANCE BETWEEN 1500 2500 OHMS FOR THE BENDIX WS 20 SPEED SENSOR YES REPLACE THE SENSOR NO NO GO TO SECTION III INSPECTION FOR ILLUMINATED LED s NO START HERE FROM SECTION VI PART A GO TO SECTION III INSPEC TION FOR ILLUMINATED LED s SAME LED s ILLUMINATED NO YES RECONNECT CONNECTOR AT SPEED SENSOR AND EC 12 CONTROLLER PASS MAGNET OVER RESET ON EC 12 CONTROLLER REMOVE MAGNET AND OBSERVE LEDs IGNITION OFF SERVICE BRAKES NOT APPLIED REMO
12. T UP PROCEDURE GO TO SECTION V TESTING THE MODULATOR YES NOTE THE ILLUMINATED LEDS AND GO TO SECTION VI TESTING THE WHEEL SPEED SENSOR ON IS THIS LED ILLUMINATED YES ON TESTING SNS1 or SNS2 LEDs REPLACE THE EC 12 CONTROLLER 14 Troubleshooting SECTION IV TESTING FOR POWER TO THE EC 12 CONTROLLER TURN IGNITION OFF DISCONNECT 14 PIN WIRE HARNESS CONNECTOR FROM EC 12 CONTROLLER START HERE VOLTAGE SAME AS BATTERY VOLTAGE MUST BE BETWEEN 8 AND 17 VOLTS RECONNECT CONNECTOR TO EC 12 CONTROLLER CHECK THE VEHICLE WIRING FOR CONTINUITY REFER TO THE VEHICLE SERVICE MANUAL AND CHECK THE BATTERY VOLTAGE REPAIR OR REPLACE AS NECESSARY AND REPEAT THE INITIAL START UP PROCEDURE YES NO MAGNET HERE PERFORM A MAGNETIC RESET BY PASSING A MAGNET OVER THE RESET IN EC 12 CONTROLLER DIAGNOSTIC WINDOW THEN REMOVE MAGNET TURN IGNITION OFF DO NOT APPLY BRAKES RECONNECT WIRE HARNESS TO EC 12 CONTROLLER TURN IGNITION ON amp APPLY amp HOLD BRAKES ON IS THE RED VOLT LED STILL ILLUMINATED TURN IGNITION ON MAKE amp HOLD A BRAKE APPLICATION AND MEASURE VOLTAGE BETWEEN POWER AND GROUND PINS ON WIRE HARNESS CONNECTOR A to C B to C RESETTING EC 12 CONTROLLER CHECKING VOLT LED ON ON REPLACE EC 12 CONTROLLER REPEAT THE INITIAL START UP PROCEDURE YES NO A B C D E F G H J K L M N P POWER A amp B GR
13. VE 14 PIN CONNECTOR FROM EC 12 CONTROLLER MEASURE RESISTANCE BETWEEN SPEED SENSOR PINS M amp L AND N amp P ON CONNECTOR RESISTANCE FOR BENDIX WS 20 SPEED SENSOR IS BETWEEN 1500 2500 OHMS REFER TO VEHICLE MANUAL FOR THE RESISTANCE VALUES IF OTHER THAN WS 20 SPEED SENSOR IS IN USE REPAIR OR REPLACE SPEED SENSOR WIRING HARNESS AND REPEAT THE INITIAL START UP PROCEDURE A B C D E F G H J K L M N P M SNS 2 L SNS 2 N SNS 1 P SNS 1 TESTING SPEED SENSOR RESISTANCE MAGNET HERE RESETTING EC 12 CONTROLLER EC 12 CONTROLLER WIRE HARNESS CONNECTOR 18 NOTES amp REFERENCES MC 12 MODULATOR CONTROLLER ASSY TRAILER SERVICE AIR LINE SPEED SENSOR EXCITER RING SPRING BRAKE VOLT LED red High Low Voltage MOD LED red M 12 Modulator Failure SNS1 LED red Wheel Sensor Failure SNS2 LED red Wheel Sensor Failure CONT LED red EC 12 Controller Failure 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 E F G H J K L M N P SENSOR 1 SNS 1 SENSOR 2 SNS 2 SENSOR 1 SNS 1 SENSOR 2 SNS 2 OPTIONAL TRACTOR MOUNTED STATUS LIGHT OPTIONAL CONSTANT POWER TRACTOR IGNITION OPTIONAL TRAILER MOUNTED STATUS LIGHT STOPLIGHT SWITCH POWER 14 PIN EC 12
14. eral 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 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 engine be in operation EXTREME CAUTION should 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 Use only the proper 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 make certain to drain the air pressure from 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 recommended procedures 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 press
15. esponding to the failure mode will illuminate A failure is stored in memory until the problem is repaired and the EC 12 controller is reset NOTE Only the voltage LED resets itself after the condition no longer exists 9 TROUBLESHOOTING INFORMATION PREPARATION FOR TESTING All trailer antilock testing should be performed with a tractor connected to the trailer 1 Connect the tractor to the trailer and build up the air system on both the tractor and trailer to governor cut out pressure 2 Park the combination on a level surface Apply the tractor parking brakes then release the trailer parking brakes only and turn off the engine NOTE Some tractors may not have the ability to release the trailer brakes while the tractor parking brakes remain applied In this event chock all wheels build the tractor and trailer system to governor cut out and turn off the engine without applying the parking brakes TROUBLESHOOTING GENERAL While the EC 12 controller diagnostic display locates a specific problem area it is still necessary to confirm whether the problem resides in the component itself or the wiring Basically the troubleshooting procedure that follows is devoted to narrowing the problem to either the wiring or a specific antilock component It should be noted that ALL TROUBLESHOOTING BEGINS BY OBSERVING THE ANTILOCK STATUS LAMP ON THE TRAILER WHILE PERFORMING THE INITIAL START UP PROCEDURE and following the direc
16. leakage No leakage is permitted 5 If leakage is excessive around the supply and exhaust solenoids replace the M 12 modulator If excessive leakage is detected where the solenoid assembly and M 12 modulator body meet replace the M 12 modulator If excessive leakage is detected at the exhaust port before replacing the M 12 modulator perform the following test Place the vehicle in park by exhausting the air pressure from the emergency side of the spring brake Perform the leakage check around the exhaust If the air continues to leak out the exhaust replace the M 12 modulator If a leak exists between the emergency and service sides of the spring brake the leakage at the exhaust will cease when air pressure is exhausted from the emergency side of the spring brake The air pressure will pass from the emergency side to the service side of the chamber out the service inlet and out the M 12 modulator exhaust ELECTRICAL TEST If the status light remains on after the trailer brakes have been actuated inspect the EC 12 controller for illuminated LEDs Each LED represents a specific area VOLT LED red High Low Voltage MOD LED red M 12 Modulator Failure SNS1 LED red Wheel Sensor Failure SNS2 LED red Wheel Sensor Failure CONT LED red EC 12 Controller Failure PWR LED green EC 12 Controller Power RED LEDs INDICATE FAILURE When the EC 12 controller senses a failure the red LED corr
17. lean all old thread sealant from the pipe threads Any component exhibiting a condition described in inspection steps 2 to 5 should be discarded and replaced before proceeding ASSEMBLY REFER TO FIG 9 1 Using a lubricant Bendix Pc No 291126 lightly coat all o rings and the bores of the valve body 2 Install spring seat 9 onto the inlet exhaust valve 8 so that it covers the rubber seat of the inlet exhaust valve Place the inlet exhaust valve large diameter first into the M 12 modulator s bottom bore 3 Install spring 10 over the barrel of the inlet exhaust valve 8 so that one end of the spring rests on the spring seat 9 4 Install the o rings 11 8 12 into the respective grooves of the O D and l D of the exhaust assembly 13 Place the large diameter of the exhaust assembly against the spring 10 and compress the spring until the exhaust assembly enters the bore of the body and the o ring 11 seals against the wall of the bore 5 Depress the exhaust assembly into the bore until it exposes the groove for the snap ring 14 Install snap ring 14 into its groove Make sure it is fully seated 6 Install o ring 5 into its groove in the piston 6 Install piston 6 into the M 12 modulator body The piston stem fits into the small hole in the center of the body 7 Install o ring 4 onto the protrusion on the bottom of the M 12 modulator solenoid assembly Install the solenoid assembly 2
18. ock up during aggressive braking Like Bendix s tractor antilock the trailer system can provide single or tandem axle control The main component is nipple mounted to a reservoir so the system requires no special trailer modifications The trailer antilock system consists of the following MC 12 modulator controller WS 20 wheel speed sensors electrical connectors and wiring The MC 12 modulator is the main component It houses the EC 12 electronic controller and the M 12 modulator which contains solenoids and a standard relay valve The EC 12 controller houses the electronics that regulate the trailer antilock system and also incorporates a diagnostic display window and a 14 pin connector The EC 12 controller mounts to the M 12 modulator with four bolts and it is internally connected to the solenoids by a four pin connector The solenoids are the interface between the EC 12 controller electronic signals and the pneumatically operated modulator Sensors mounted at the DIAGNOSTIC DISPLAY DIAGNOSTIC DISPLAY DELIVERY PORTS 2 VERTICAL 2 HORIZONTAL CONTROL PORT 14 PIN CONNECTOR EC 12 CONTROLLER M 12 MODULATOR DELIVERY PORTS 4 VERTICAL 2 FIGURE 2 MC 12 MODULATOR TRAILER SYSTEM WIRING SCHEMATIC Seven Conductor Antilock Wire Gauge Pin Wire Connector Wire Single Connector No Letter Color Lamp and Signal Circuits Dolly Double Triple 1 1 C White G
19. onto the valve body The solenoid assembly will fit on the M 12 modulator body in any of four orientations 90 degrees apart However if clearance is a problem make sure the control port is not directly above the valve s supply port which will be nipple mounted to a reservoir Secure the solenoid assembly to the valve body with the four 1 2 bolts Torque the bolts to 120 150 in Ibs 8 Install gasket 7 onto the EC 12 controller Install the EC 12 controller 1 as shown in Figure 9 by plugging the electrical connector from the solenoid assembly into the socket in the bottom of the controller Press in until lock tab engages Ensure engagement by pulling the connector lightly Place the 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 brakes 2 Make several trailer brake applications and check for prompt application and release at each wheel 3 Check for inlet valve o ring leakage With the trailer 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 4 Check for exhaust valve leakage With the trailer service brakes fully applied coat the exhaust port with a soap solution A 1 bubble in 3 seconds is permitted Coat the outside of the modulator body to check for seal ring
20. round Return To Towing Vehicle 12 10 8 2 2 Black Clearance Side Marker and Identification Lamps 12 12 12 3 3 Yellow Left Hand Turn Signal and Hazard Signal Lamps 12 12 12 4 4 Red Stop Lamps 10 10 10 5 5 Green Right Hand Turn Signal and Hazard Signal Lamps 12 12 12 6 6 Brown Tail Clearance Side Marker and License Plate Lamps 12 12 12 7 7 B Blue Auxiliary Dome Etc or constant Antilock power 12 12 12 4 9 A Red Antilock Power From Stop Lamp 10 10 10 8 D Yellow Trailer Mounted Status Light 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 12 modulator during trailer operation Trailer Mounted Status Indicator Marker Marker Marker Marker Clearance Clearance Wheel Speed Sensor Marker Marker Rear 7 Pin Connector Plug See Note Wheel Speed Sensor CI Directional CI Directional Stop amp Tail Stop amp Tail License Plate Note The rear 7 pin connector plug is for Dolly operations for Doubles amp Triples To Pin G on MC 12 Modulator Connector To Power Side of Tractor Ignition Tractor Electrical Relay Tractor Dash Mounted Trailer Antilock Status Lamp The relay illustrated to the right is used when a tractor dash mounted stat
21. terior 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 E
22. tions contained in the procedure Be sure to record a failure before resetting the system Reset by holding a magnet capable of picking up 3 ounces over the reset location on the diagnostic window If the LED s do not clear during a reset check all wiring and hardware per the troubleshooting chart BWS 1082 During a reset all LEDs will illuminate until the magnet is removed IMPORTANT TROUBLESHOOTING TIPS 1 Record all findings and the action taken during the troubleshooting process The record sheet should be filed in the trailer maintenance folder for future reference and comparison 2 No voltage or resistance tests are performed into the EC 12 controller All voltage and resistance tests are performed by beginning at the wire harness half of the connector and moving AWAY from the EC 12 control ler toward an antilock system component modulator wheel speed sensor etc NOTHING ON GO TO SECTION IV GO TO SECTION IV NOT ON GO TO SECTION IV ONE OR BOTH ON GO TO SECTION VIA ON GO TO SECTION V DIAGNOSTIC DISPLAY QUICK REFERENCE This index is presented for the benefit of personnel experienced in troubleshooting Bendix MC 12 trailer antilock system It provides a quick reference to specific sections that provide testing procedures and values 10 START HERE STATUS LAMP DOES NOT BLINK COMES ON AND REMAINS ILLUMINATED YES NO STATUS LAMP COMES ON BLINKS AND GOES OUT THE SYSTEM IS
23. ure 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 FIGURE 8 ELECTRICAL CONNECTOR A B C D E F G H J K L M N P SENSOR 1 SNS 1 SENSOR 2 SNS 2 SENSOR 1 SNS 1 SENSOR 2 SNS 2 OPTIONAL TRACTOR MOUNTED STATUS LIGHT OPTIONAL CONSTANT POWER TRACTOR IGNITION GROUND STOPLIGHT SWITCH POWER OPTIONAL TRAILER MOUNTED STATUS LIGHT 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 ex
24. us lamp for the trailer antilock system is desired Like the trailer mounted status lamp this is an option and is not required 3 System ground pin 1 on the seven pin connector white enters the MC 12 modulator at pin C Each wheel speed sensor sends the MC 12 modulator its AC signal through a pair of wires The MC 12 modulator pins for the sensors are L M and N P The MC 12 modulator can send a 12v failure signal to the optional trailer mounted status light through pin D The status light indicates the condition of the trailer antilock system In addition the MC 12 modulator can send a grounding signal through its pin J to an optional tractor dash mounted status lamp During start up when the trailer brakes are actuated trailer antilock immediately runs a self check The status light flashes once and then goes off Should a problem occur the antilock system disengages and returns to normal R 12 relay valve operation If the status light comes 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 PEAK TO PEAK HIGH SPEED LOW SPEED directs the driver to the problem area A series of LEDs on the EC 12 controller indicate the status of power EC 12 controller wheel speed sensors M 12 modulator solenoids or voltage level OPERATION
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