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Section 6

! To prevent serious eye injury, always wear safe eye protection when you perform vehicle maintenance or service.

When welding on an ABS-equipped vehicle it is necessary, disconnect the power connector from the ECU.

1. Follow the vehicle manufacturer’s instructions to back off the slack adjuster and remove the tire, wheel and drum.
2. Hold the sensor, not the cable, and use a twisting motion to pull the sensor out of its mounting block.
3. Remove the spring clip from the mounting block.
4. Remove any fasteners that hold the sensor cable to other components.
5. Disconnect the sensor cable from the extension cable.

Sensor locations vary according to suspension types. Typically, a spring suspension has sensors on the forward axle, and an air suspension has sensors on the rear axle.

1. Apply a mineral oil-based grease that contains molydisulfide to the sensor spring clip and to the body of the sensor. The grease must be anti-corrosive and contain adhesive properties that will continuously endure temperatures from –40º to 300ºF (-40º to 150ºC).2. Push the spring clip into the sensor holder from the inboard side, until the spring clip tabs are against the sensor holder. Push the sensor into the spring clip as far as possible. Refer to Figure 6.1.

Figure 6.1

3. Route the sensor cable toward the brake chamber, over the brake spider, and behind the axle. Secure the cable to the axle between the brake spider and the suspension brackets. Continue to route the sensor cable behind the spring seats. Secure the cable to the axle one inch from the molded sensor plug. Refer to Figure 6.2.

Figure 6.2

4. Install the wheel hub carefully, so that the tooth wheel pushes against the sensor as you adjust the wheel bearings.  After installation there should be no gap between the sensor and the tooth wheel.  During normal operation a gap of 0.040-inch is allowable.

5. Sensor Output Voltage Test:  Use a volt/ohm meter to check the AC output voltage of the sensors while rotating the wheel at approximately one-half revolution per second.  Minimum output must be greater than 0.2 volts AC.  If minimum output is less than 0.2 volts AC, push the sensor toward the tooth wheel.  Recheck the sensor output.

ABS Relay Valve 

Figure 6.3

! WARNING

Release all pressure from the air system before you disconnect any components.  Pressurized air can cause serious personal injury.

How to Remove a Standard ABS Relay Valve

! CAUTION

1. Release all pressure from the air system.

2. Disconnect the cable from the valve.

3. Attach labels to identify all of the air lines.

4. Disconnect the air lines from the valve.

5. Remove the mounting fasteners if the valve is not nipple-mounted directly to the air tank.

6. Remove the valve.

How to Install a Standard ABS Relay Valve

! CAUTION

You must use Schedule 80 pipe nipple (3/4-inch NPTF) to nipple-mount the ABS relay valve securely to the reinforced air tank to avoid possible serious personal injury and damage to components.

1. Install the valve with two lock nuts and washers as required.  Tighten the hex nuts to a torque of 18 lb-ft (24 N*m) or nipple-mount the valve directly to the air tank with Schedule 80 pipe nipple (3/4-inch NPTF).

2. Connect the air lines to the ports according to the labels installed when the air lines were disconnected.

3. Connect the cable to the valve.

4. Pressurize the brake system.  Apply the brakes and verify there are no air leaks.

The ECU and valve assembly are sealed together as one unit. To ensure product integrity and avoid possible damage to the components, do not attempt to separate the ECU from the valve.

1. Release all pressure from the air system.

2. Attach labels to identify all air lines.

3. Disconnect the air lines from the ECU/Valve Assembly.

4. Disconnect the power cable, diagnostic cable, additional relay valve cable (if used), and all sensor cables from the ECU/Valve Assembly. Refer to Figure 6.4.

5. Remove the ECU/Valve Assembly from its mounting location:

6. If the assembly being replaced is under warranty, please return it to the trailer OEM for replacement.

How to Install the ECU/Valve Assembly

NOTE:  The ECU/Valve Assembly is supplied with black caps on each sensor connector.

NOTE:  When a sensor cable is not plugged into a sensor connector, the black cap must remain on the connector to protect it from dirt and contamination. Figure 6.4

Figure 6.4

1. Release all pressure from the air system.

2. Attach labels to identify all air lines.

3. Disconnect the air lines from the ECU/Valve Assembly.

4. Disconnect the power cable, diagnostic cable, additional relay valve cable (if used), and all sensor cables from the ECU/Valve Assembly. Refer to Figure 6.4.

5. Remove the ECU/Valve Assembly from its mounting location:

Nipple-mounted to Air Tank: Unscrew the assembly from the air tank

! CAUTION

You must use Schedule 80 pipe nipple (3/4-inch NPTF) to nipple-mount the ECU/Valve Assembly securely to the reinforced air tank to avoid possible serious personal injury and damage to components.

Tank Mounted

! WARNING

You must use Schedule 80 pipe nipple (3/4-inch NPTF) to nipple-mount the ECU/single modulator valve securely to the reinforced air tank to avoid possible serious personal injury and damage to components.

1. Use a 3/4-inch Schedule 80 hew nipple to attach ECU/single modulator valve assembly to a reinforced air tank.  Do no overtighted.

NOTE:  Meritor WABCO does not recommend use of a vise when installing the hex nipple.  Use of a vise may cause overclamping.  Overclamping may damage the internal components of the ECU/single modulator valve assembly.

2. Use a 3/4-inch pipe plug to plug unused supply port    (Port 1).  Apply SAE-standard , DOT-approved Teflon tape or paste-type thread sealant to all pipe threads beyond the first two threads.  Pipes with pre-applied thread sealant may also be used.

3. Rotate and tighten the ECU/single modulator valve assembly until the exhaust port faces down and the connection is secure.  Usea torque wrench or rathchet with extension at the 3/4 inch pipe plug installed on the front supply port (Port 1).  Figure 6.5.

Figure 6.5

Bracket-Mounted to Cross Member of Vehicle (2S/1M Basic)

1. Install a 3/4-inch NPTF fitting in supply port (Port 1).  Use a 3/4-inch pipe plug to plug unused supply port (Port 1).

Use a 3/4-inch pipe plug to plug unused supply port (Port 1).  Apply SAE-standard , DOT-approved Teflon tape or paste-type thread sealant to all pipe threads beyond the first two threads.  Pipes with pre-applied thread sealant may also be used.

2. Attach mounting bracket to vehicle cross member midway between the side rails, close to the brake chambers the valve serves.

3. Use two 3/8-inch Grade 8 bolts with prevailing torque nuts and washers to attach assembly to the vehicle cross member.  Tighten bolts to 18 lb-ft (24 N*m).

Mounted to Cross Member of Vehicle-- Standard and Premium Mounting Bracket Not Supplied

NOTE:  When mounting the ECU/dual modulator valve assembly to the trailer cross member, refer to SAE specification J447, Prevention of Corrosion of Motor Vehicle Body and Chassis Components.  Follow all recommendations and procedures.  Your supervisor should have a copy of this specification.  Figure 6.6

Figure 6.6

1. Install a 3/4-inch NPTF fitting in supply port.  Use a 3/4-inch pipe plug to plug unused supply port (Port 1).

Apply SAE-standard, DOT-approved Teflon tape or paste-type thread sealant to all pipe plugs beyond the first two threads.  Pipes with pree applied thread sealant may also be used.

2. Use two 3/8-inch Grade 8 bolts with prevailing torque nuts to attach assembly.  Tighten bolts to 18 lb-ft (24 N*m).

3. Connect the air lines to the ports.  Follow the label markers installed when the air lines were disconnected.

4. Connect the sensor cables, external relay valve cable (if used), and power or power/diagnostic cable to the ECU/Valve Assembly.  Use the black protective connector caps included with the replacement assembly to cover unused cable connectors.

5. Perform End of Line Check before returning the trailer to service.

Replacing the ECU or Modulator Valve

With Enhanced Easy-Stop, the ECU and modulator valve may be replaced individually.  To do this, follow the instructions for removing the complete assembly, then remove the valve from the ECU.

NOTES:

For 2S/1M installations where the valve is  readily accessible, it may not be necessary to remove the entire assembly to replace the valve.

For 2S/1M bracket-mounted installations, the bracket does not need to be removed to replace the ECU or valve.

2S/1M Basic Only

To separate the ECU from the bracket, loosen and remove the three hex nuts from the underside of the bracket.  These three hex nuts hold the assembly together.

To separate the bracket from the valve, remove the three hex nuts.

Figure 6.7

To attach the ECU to the bracket, tighten the three hex nuts to 6 lb-ft (8 N*m).

To attach the valve to the bracket, tighten the three hex nuts to 12 lb-ft (16 N*m).

All Standard and Premium Installations

Loosen and remove the four hex nuts holding the assembly together.

Figure 6.7

To attach the valve to the ECU, tighten the four hex nuts to 5 lb-ft (6 N*m).

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