Bendix MC-11 TRACTOR ANTILOCK User Manual
®
Bendix® MC-11™ Tractor AntiLock
SD-13-4761
DELIVERY
FIGURE 1
14-PIN
CONNECTOR
CONTROL
SUPPLY
LED DIAGNOSTIC
DISPLAY
™
EC-11
CONTROLLER
DELIVERY
™
M-12
MODULATOR
DESCRIPTION
The Bendix® MC-11™ tractor antilock assembly is designed
to improve vehicle stability by reducing wheel lock-up during
aggressive braking. Like the MC-10™ antilock assembly that
it replaces, the MC-11™ tractor antilock assembly is a
one-channel system–it uses one modulator. And the system
can control single or tandem axles. The antilock assembly
mounts to the vehicle frame and usually replaces the drive
axle service relay valve.
The MC-11™ tractor antilock assembly consists of an EC-11
electronic controller and an M-12™ modulator. The EC-11
controller houses the electronics that regulate the antilock
system. The electronics are protected by a self-healing
silicone compound. The EC-11™ controller contains a
diagnostic window and reset switch, and its 14 pin connector
is the electrical link to the rest of the antilock system. (See
Figure 2.) The controller mounts to the modulator with four
cap screws, and it is electrically connected to the modulator
with a four-pin connector. The M-12™ modulator has two
components: solenoids, which rapidly apply and exhaust
air during an antilock stop, and a standard relay valve. (See
SD-13-4772 for more information on the M-12™ modulator.)
The air connections for the MC-11™ tractor antilock assembly
are as follows:
AIR CONNECTION EMBOSSED
™
™
Supply
IDENTIFICATION
(to reservoir) SUP
Delivery
(to brake actuator) DEL
Control
(to rear service brake valve delivery) CON
1
14 PIN CONNECTOR CALLOUTS
PIN CONNECTION
A “+” POWER
B RETARDER DISABLE
C “-” GROUND
D DASH LIGHT
E SERIAL LINK
F SERIAL LINK
G UNUSED
H UNUSED
J UNUSED
K UNUSED
L SENSOR
M SENSOR
N SENSOR
P SENSOR
14-PIN CONNECTOR
GROUND
DASH LIGHT
EXH. BLK. PWR
EXH. WHT. PWR
POWER
RETARDER
EXH. BLK. GRD
EXH. WHT. GRD
SENSOR
SERIAL LINK
FIGURE 2 - TYPICAL MC-11™ TRACTOR ANTILOCK WIRING SCHEMATIC
2
14-PIN
CONNECTOR
SENSOR
EXHAUST
SOLENOID
INLET SOLENOID
RESERVOIR
SUPPLY
BRAKE
VALVE
CONTROL
PISTON
DELIVERY
DOUBLE
CHECK VALVE
TRAILER
CONTROL
VALVE
EXHAUST
FIGURE 3 - APPLYING: NORMAL SERVICE APPLICATION
The wiring connections on the 14 pin connector are as
follows:
PIN A - Power PIN IF - Serial Link
PIN B - Retarder Disable PIN L - Sensor
PIN C - Ground PIN M - Sensor
PIN D - Dash Light PIN N - Sensor
PIN E - Serial Link PIN P - Sensor
PIN A - Vehicle power is supplied to the EC-11™ controller
from the ignition switch, through a fuse, to pin A on
the 14 pin connector.
PIN B - The EC-11™ controller is equipped with a retarder
disable circuit, which, when coupled with an
electrical relay, will disable the vehicle retarder
(engine or transmission) during an antilock stop.
The retarder disable function is not essential but is
highly recommended for vehicles equipped with a
retarder. Connection to pin B on the EC-11
™
controller provides this function.
PIN C - Pin C connects directly to negative vehicle ground.
PIN D - A dash light and its electrical relay are controlled
by the EC-11™ controller through pin D. The light
advises the driver of the antilock system condition.
BRAKE
CHAMBER
PIN E - The serial link allows the EC-11™ controller to “report”
its operating PIN IF condition to a specialized
external computer in response to certain commands
it receives. The serial link configuration conforms to
S.A.E. standard J1708. Pins E and F provide serial
link connections to the EC-11™ controller, but the
function is not essential for MC-11™ tractor antilock
assembly operation.
PIN L - Sensors mounted at the wheel end send wheel
speed information PIN M to the EC-11™ controller
through pins L-M and N-P. The EC-11™ controller
receives the information at (PIN N) 100 pulses per
wheel revolution.
The MC-11™ tractor antilock assembly “knows” what’s
happening at the wheel ends because of the signals it
receives from the wheel speed sensors. The sensors are
actually A.C. generators. They create a magnetic field; and
when the field is interrupted by an irregular surface, like a
tone ring, A.C. 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
inlet solenoid is open, and the exhaust solenoid is closed.
In this condition, the M-12™ modulator is a regular R-12
relay valve. It receives a control signal from the foot valve,
™
3
EXHAUST
SOLENOID
BRAKE
VALVE
DOUBLE
CHECK VALVE
TRAILER
CONTROL
VALVE
INLET SOLENOID
RESERVOIR
SUPPLY
EXHAUST
FIGURE 4 - BALANCED POSITION
which passes through the open inlet solenoid and into the
control cavity of the relay valve. The valve then applies air to
the service brake chambers in proportion to the control signal.
If wheel lock is impending, the EC-11™ electronic controller
commands the solenoids to modulate brake chamber
pressure on the axles in which the system is installed.
OPERATION
APPLYING: Normal Service Application
When a normal service brake application is made, 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.
BALANCED POSITION: Normal Service Application
CONTROL
PISTON
DELIVERY
BRAKE
CHAMBER
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-11
controller senses impending wheel lockup, it will command
the antilock system to alter the service brake application
automatically.
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.”
™
The modulator reaches a balanced position when control
pressure acting upon the topside 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
4
PREVENTIVE MAINTENANCE
GENERAL
Perform the inspections and tests at the prescribed intervals.
If the MC-11™ tractor antilock assembly fails to function as
described, repair or replace the unit.
EVERY 3 MONTHS; 25,000 MILES; 900 OPERATING
HOURS; OR DURING THE VEHICLE CHASSIS
LUBRICATION INTERVAL
EXHAUST
SOLENOID
DOUBLE
CHECK VALVE
TRAILER
CONTROL
VALVE
BRAKE
VALVE
INLET SOLENOID
RESERVOIR
SUPPLY
EXHAUST
FIGURE 5 - EXHAUSTING: NORMAL SERVICE APPLICATION
1. Remove any accumulated contaminants and visually
inspect the exterior of the unit for excessive corrosion or
physical damage.
2. Inspect all air lines and wiring connected to the MC-11
tractor antilock assembly for signs of wear or physical
damage. Replace as necessary.
3. Perform “LEAKAGE TEST.”
EVERY YEAR; 100,000 MILES; OR 3,600 OPERATING
HOURS
1. Perform “OPERATIONAL AND LEAKAGE TESTS.”
OPERATIONAL AND LEAKAGE TESTS
LEAKAGE TEST
1. Park the vehicle on a level surface and block the wheels.
Release the parking brakes and build the air system to
full pressure.
2. Turn the engine OFF and make 4 or 5 brake applications.
Note that the service brakes apply and release promptly.
3. Build system pressure to governor cut-out and turn engine
OFF.
4. Make and hold a full service brake application.
A. Apply a soap solution to the relay valve exhaust port.
A 1" bubble in 3 seconds is permitted.
B. Apply a soap solution to the outside of the modulator
body where the relay valve joins the solenoid
assembly. A 1" bubble in 3 seconds is permitted.
CONTROL
PISTON
DELIVERY
BRAKE
CHAMBER
5. If leakage is excessive around the supply and exhaust
solenoids, replace the M-12™ modulator.
OPERATIONAL TEST
™
LED Operation
Although the MC-11™ assembly has self-check diagnostics,
the LEDs (Light Emitting Diodes) should be inspected to
ensure that they are functioning properly. With the vehicle
ignition on, hold a magnet (capable of picking up 3 ounces)
to the RESET position on the diagnostic window. All LEDs
should illuminate. If one or more of the LEDs do not
illuminate, and the dash light indicates proper system
function, note the nonilluminated LEDs for future reference.
Diagnostic capabilities will be limited, but the system will
continue to function as designed.
Solenoid Operation
The MC-11™ assembly monitors the system electronics upon
vehicle start-up. However, the vehicle should be tested to
verify proper solenoid function. Two technicians will be
required to properly test the solenoids.
1. Park the vehicle on a level surface and block the wheels.
Release the parking brakes and build the air system to
full pressure.
2. Turn the engine ignition key to the OFF position. Then
make and hold a full brake application.
5
EXHAUST
SOLENOID
DOUBLE
CHECK VALVE
TRAILER
CONTROL
VALVE
BRAKE
VALVE
INLET SOLENOID
RESERVOIR
SUPPLY
EXHAUST
FIGURE 6 - ANTILOCK MODE: SOLENOIDS ACTIVATED
3. With the brake application held and a technician near
the modulator, turn the vehicle ignition key to the ON
position. One short burst of air should be noted from the
modulator exhaust. If one short burst of air is not noted,
or if the exhaust is prolonged and not short, sharp and
well-defined, refer to the troubleshooting section.
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURY OR 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.
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.
CONTROL
PISTON
DELIVERY
BRAKE
CHAMBER
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 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.
™
6
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