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Figure 10 - Relay Valve

Out

(3/8" Delivery Port to

Brake Chamber)

3/8" Control Port

3/4" Supply Port

Three-Pin

ECU Connector

Relay Valve

The trailer ABS relay valve controls air pressure to individual

brake assemblies, and functions as a standard relay valve

when there are no ABS control signals. Depending on the

particular ABS configuration, a system may utilize one or

two relay valves. See Figure 10.

Each relay valve contains two solenoids for air control. The

hold solenoid maintains air pressure; the release solenoid

removes pressure from the brake. The Electronic Control

Unit signals the relay valve(s) for air hold and release by

activating the appropriate solenoid.

Each relay valve has a three-pin terminal for connection to

the Electronic Control Unit.

Delivery Ports

Both 2-port and 4-port versions of the relay valve are

available. These are all tapped for 3/8 NPT fittings.

Crack Pressure

Standard valves are available with 4.0 PSI ±0.5 PSI crack

pressure. Other crack pressures can be provided. For

example, 6.0 PSI valves may be used with wedge brakes.

Bracket, Valve, ECU combinations

Various combinations of mounting brackets, ECUs and

valves are available preassembled to facilitate system

installation on a variety of vehicles. Refer to the Bendix

A-18

™

trailer ABS Illustrated Parts List for further

information.

Port Orientation

If necessary, the control and supply ports of the valve can

be reoriented with respect to each other. Remove the four

assembly bolts. Rotate top with respect to bottom as

required. Use care to maintain cleanliness of valve interior.

Retorque bolts to 10.0 lb-ft (13.6 N•m). Do not exceed

12.0 lb-ft (16.3 N•m).

Pipe Fitting Torques

Refer to the following torque specifications when installing

pipe nipples. Torques are for NPT threads with thread

sealant applied. Do not use thread tape. Contamination

by thread tape can cause component failure.

Tighten pipe nipples as follows:

• With Thread Sealant - Finger tight plus 1 1/2 turns

• Without Thread Sealant - Finger tight plus 2 turns

Clamping

A fixture may be necessary to hold the relay valve when

reorienting ports or when attaching fittings. If a vise is used,

there is a potential danger of distorting the barrel and piston

within the valve rendering the valve inoperative. It is

recommended that a fixture be used that avoids the

potential for stressing the valve.

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.

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.

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BENDIX BW2262 Manuale Utente Pagina 12

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