BENDIX BW1742 User Manual

Troubleshooting The Bendix MC-12 Trailer AntiLock System (Pre-2/98)

3 PIN STYLE

CONNECTOR

Ground Stop Light Power Status Light

STATUS INDICATOR

(Optional)

Ground

Constant

Power

Stop Lamp

Power

IF INDICATOR REMAINS ILLUMINATED

SYSTEM REQUIRES SERVICE

ANTILOCK

INDICATOR

7 PIN CONNECTOR

Back

Front

Connector

MC-12 Modulator

Controller

(Ref SD-13-4762)

WHEEL SPEED SENSOR

CONNECTOR

Resistance Across Pins

1500 - 2500 ohms (Ref. SD-13-4754)

OPERATIONAL INFORMATION

The EC-12 controller houses the electronics that regulate the antilock system. The EC-12 contains a diagnostic window and a 14 pin connector.

Diagnostic Window

The EC-12 mounts on the M-12 modulator with four bolts and it is internally connected to the solenoids by a four pin connector. Sensors mounted at the wheel end send wheel speed information to the EC-12 through the 14 pin connector. If wheel lock up is impending, the EC-12 commands the solenoids to modulate brake chamber pressure on the axle(s) on which the system is installed. The MC-12 modulator controller receives power from the 7 pin, tractor to trailer, connector at the nose of the trailer. The ground connection to the EC-12 is also from the 7 pin connector. During start up, when the trailer brakes and stop lights are actuated, trailer antilock immediately runs a self check. The trailer status light, if so equipped, flashes once and then goes off. Should a problem occur, the status light comes on and remains on.

Wheel Speed

Sensor

TYPICAL TRAILER

AXLE

Mounting

Block

Tie Wrap

TROUBLESHOOTING

If the status light remains on with power applied, inspect the EC-12 for illuminated LEDs. The status light is an optional feature in the trailer antilock system. If no status light is present, the diagnostic LEDs should be checked periodically.

Reset controller with magnet after repair.

IF THESE LED'S

ARE ILLUMINATED

CHECK THE VEHICLE WIRING HARNESS CONNECTOR

FOR THE PROPER RESISTANCE WITH

STOP LAMP POWER OFF

MC-12 Controller Cable Assembly

Status Light Stop L. Power

Ground *Constant Power

To Controller

SENSOR 1

SENSOR 2

MODULATOR

VOLTAGE

w/STOP

LAMP

POWER

P N M L K J H G F E D C B A

N - P 15 - 2500 Ohms

P N M L K J H G F E D C B A

L - M 15 - 2500 Ohms

9.5 - 11.5 Ohms

White to White

P N M L K J H G F E D C B A

9.5 - 11.5 Ohms

Black to Black

Sensor 2 Sensor 2

Old

Style

New

Style

Sensor 1 Sensor 1

*Old Style Connectors do not have a Constant Power terminal

Vehicle wire harness

Most Commonly Encountered Problems That Result In LEDs Being Illuminated.

Repair or Replace Components As Necessary

• Damaged connectors or wires, caused by dangling or loose wires not properly restrained.

• Power connection not capable of supplying 12 volts at 3 amps because of a poor connection,

bad crimp.

• Corroded connectors and connections not properly sealed or seated.

• Terminals not completely latched or sealed into connectors; harness connector bolt not tight.

• Improperly spliced connection repair or repair not sealed properly.

• Excessive sensor air gap, sensor bushing tension or excessive bearing end play

(Gently push sensor against exciter ring, or readjust bearings).

• Non functioning antilock components, sensor, controller, modulator.

Additional Servicing Tips

• Gently probe terminals when checking for resistances, do not deform contacts.

• Apply nonconductive dielectric grease to any and all connectors if

inspecting or disconnecting connectors.

• If excessive cable length is present, bundle and tie wrap

neatly to adjacent air lines or framing members.

• Do not pierce wires with probes when

roubleshooting harnesses.

CONTROLLER

ECU

A - C 9 to18 Volts DC

B - C 9 to18 Volts DC

Replace Controller

ALL CONTACT OF THE 14 PIN CONNECTOR ABOVE SHOULD NOT HAVE ANY CONTINUITY TO THE GROUND CONTACT "C" CONTACTS "A" & "B" ARE POWER TO THE MC-12.

ADDITIONAL INFORMATION:

1-800-247-2725