BENDIX BW1959 User Manual

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

A Stop Lamp Power B Constant Power C In Cab Status Light D Trailer Status Light E Ground

STATUS INDICATOR

Ground

Constant

Power

Stop Light

Power

In Cab Status

Light

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) in which the system is installed. The MC-12 modulator controller receives power and ground from the vehicles electrical system. During start up, trailer antilock immediately runs a self check. The trailer status light flashes once and then goes off. Should a problem occur, the status light comes on and remains on.

TROUBLESHOOTING

If the status light remains on, inspect the EC-12 for illuminated LEDs. If no status light was installed, the diagnostic LEDs should be checked periodically.

Wheel Speed

Sensor

Mounting

Block

TYPICAL

TRAILER AXLE

Tie Wrap

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

SENSOR 1

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

N - P 15 -2500 Ohms

MC-12 Controller Cable Assembly

A Stop Lamp Power B Constant Power C In Cab Status Lamp

D Trailer Status Lamp E Ground

Sensor 2 (yellow) Sensor 2 (yellow)

To Controller

Stop Lamp Power Constant Power Ground Trailer Status Lamp Cab Status Lamp (optional)

Sensor 2 Sensor 2 Sensor 1 Sensor 1

SENSOR 2

MODULATOR

VOLTAGE

w/STOP

LAMP

POWER

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

A - C 9 to 18 Volts DC B - C 9 to 18 Volts DC

9.5 - 11.5

Ohms

Black to Black

Sensor 1 (blue) Sensor 1 (blue)

Vehicle wire harness

Most Commonly Encountered Problems That Result In LEDs Being Illuminated.

Repair or Replacement 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

• Do not pierce wires with probes when troubleshooting harnesses.

• Gently probe terminals when checking for resistances,

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 deform

ECU

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

Replace Controller

ADDITIONAL INFORMATION:

1-800-247-2725

-2-1

Visit: www.bendix.com