BENDIX A-18 TRAILER ABS User manual

1
®
SD-13-4757
GEN 4™AND GEN 5™ABS INTRODUCTION
This manual describes the Bendix®A-18™trailer ABS
system and contains two primary sections:
• Installation
• Service
The Installation section provides the information required
fortheproperinstallationofaFMVSS-121complianttrailer
air brake systems that incorporate the Bendix TrailerABS
system and complementary trailer components.
TheServicesectionofthemanualincludestheinformation
necessarytoproperlymaintain,troubleshootandrepairthe
A-18™trailerABS system.
Following the installation, service, and troubleshooting
procedures contained in this manual will produce a high
performance, long life, low maintenance antilock braking
system.
For assistance in your area call Bendix at 1-800-247-2725
or RoadRanger®at 1-800-826-4357.
Benefits of Trailer ABS
ABS-controlled trailer braking ensures optimum vehicle
stability while minimizing the stopping distance. During
vehicle operation, the trailer ABS Electronic Control Unit
(ECU)continuously monitorsallwheelspeedsensors. Data
input from the wheel speed sensors allows the ECU to:
• Detect impending wheel lock.
• Maintain optimum wheel slip.
• Maximize overall braking effectiveness.
• Minimize tendencies for trailer swing out during hard
braking conditions.
Document Revision Level
This document is subject to revision.
For updates please visit www.bendix.com.
Bendix®A-18™Trailer ABS (Gen 4™and Gen 5™ABS)
FIGURE 1 - ABS Controller Assemblies
Table of Contents
Power Requirements forABS . . . . . . . . . . . . . . . . . . . 3
GeneralAir Brake Requirements . . . . . . . . . . . . . . . . . 4
Brake Priority Options . . . . . . . . . . . . . . . . . . . . . . . . . 5
ABS Performance Characteristics . . . . . . . . . . . . . . . . 6
ABS Controlled Braking . . . . . . . . . . . . . . . . . . . . . . . . 6
ABS Component Function . . . . . . . . . . . . . . . . . . . . . . 6
Trailer ABS Configurations . . . . . . . . . . . . . . . . . . . . . 7
Sensor Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Trailer ABS Component Overview . . . . . . . . . . . . . . . . 9
Electronic Control Unit (ECU) . . . . . . . . . . . . . . . . . . 11
RelayValve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Relay Valve Operation Modes . . . . . . . . . . . . . . . . . . 14
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Install the ECU/Relay Valve and
StandAlone Relay Valve . . . . . . . . . . . . . . . . . . . . . 16
Install the Inline Power Connector . . . . . . . . . . . . . . . 17
Install the MainABS Harness . . . . . . . . . . . . . . . . . . 17
Install the Trailer Mounted Warning Light . . . . . . . . . 18
End-Of-Line Diagnostics . . . . . . . . . . . . . . . . . . . . . . 23
Use of Hand Held Tool for Configuration . . . . . . . . . . 23
Troubleshooting and Fault Codes . . . . . . . . . . . . . . . 25
Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
ServiceRanger PC Software . . . . . . . . . . . . . . . . . . . 27
ABS Valve Troubleshooting . . . . . . . . . . . . . . . . . . . . 28
Speed Sensor Troubleshooting . . . . . . . . . . . . . . . . . 29
Accessing Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Fault Code Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Bendix®is a registered trademark of Bendix Commercial
Vehicle Systems LLC.
Eaton®,RoadRanger®, and ServiceRanger®are registered
trademarks of Eaton Corporation.

2
Tractor and trailer ABS systems operate independently of
eachother. Therefore, systems will work together properly
even if they are not supplied by the same manufacturer.
Forinformationondisassembly, installation,andserviceof
relatedaxleandbrakecomponents,refer to their individual
Bendix®Service Manuals.
For assistance in your area call Bendix at 1-800-247-2725
or RoadRanger®at 1-800-826-4357.
These ABS controllers and systems were originally
marketed under the Eaton®Brand name. For more
information,contactBendix or refer toyourlocalauthorized
Bendix dealer, or RoadRanger®.
Power Requirements for ABS
Since March 1998 the trailer wiring systems provide two
sources of power for the antilock system.
The two power sources are:
1. Full-time power (when ignition is on) must be provided
by the tractor. This full-time power source may be
shared with other trailer circuits. The SAE J560 Blue
(AUX) circuit is commonly used as the full-time power
source. Inothercases,a separateISO3731connector
is provided.
2. Brakelightpoweris provided as a secondary source of
power in cases where an older tractor that does not
provide full-time power is used to operate an ABS
equippedtrailer.
The industry requires that the tractor provide at least 10
amps at 12 volts at the trailer end of the SAE J560 or ISO
cableonallABSpowercircuits. Thesespecificationsmeet
TMC RP-137 and are consistent with SAE-2247.
There are no formal requirements. However, suppliers of
TrailerABShaveagreed toprovideforproper antilockbrake
operation down to a minimum of 8.5 volts (at which time
the warning lamp will activate). A new TMC RP
(Recommended Practice) is being developed which
recommends that trailer manufacturers provide a 1.0 volt
safety margin over the 8.5 volt minimum.
Systemcurrent requirementswillnot exceed 0.5 ampsper
control unit and three amps per valve.
A-18™trailer ABS system modulators have a nominal
resistanceof5.5ohms andrequireapproximatelytwo amps
to operate. The control unit is designed to power warning
lamps with a typical current of 300mA for trailer mounted
warninglamps and 100mAforcabmountedwarninglamps.
Trailer Mounted ABS Warning Light
Rules for the location, color, labeling, intensity and
photometrics for external ABS warning lamps have been
establishedby the National Highway TransportationSafety
Administration (NHTSA). These requirements were
effective as of March 1, 1998.
Location
The lamp mounting location shall be near the left side rear
of the trailer, no closer than 150 mm (5.9 inches) and not
more than 600 mm (23.6 inches) from the rear red side
markerindicatorlamp. (Refer to Figure 22.) Onaconverter
dolly, the lamp mounting location shall be on a permanent
structure of the dolly at least 375 mm (14 inches) above
the road surface.
Color and Labeling
Themalfunctionindicatorlampmust be yellow in color and
identifiedwiththeletters “ABS” to distinguish the lamp from
other yellow side markers. The letters may be on the lens,
on the lens housing, or on the trailer itself, near the lamp.
Intensity and Photometric Requirements
TheexternalABSmalfunctionindicator lamp must conform
to SAE-J592 JUN92. Trailers shall use a combination
clearance/side marker lamps marked with a “PC” or “P2”.
These lamps offer a widely diffused beam pattern
throughout a full 180-degree left and right range.
ABS

3
FIGURE 2 - Air Timing Requirements Chart
General Air Brake Requirements
Basicdesignrequirementsfor trailer air brake systems are
setforthin FMVSS-121. FMVSS-121 covers requirements
for new construction. Once put into operation, the trailer’s
brake systems must be maintained in accord with the
following FHWA/OMC standards.
• FMCSR 393 - Covers required equipment
• FMCSR 396 - Covers inspection and repair
Air Timing Requirements
FMVSS-121 specifies the maximum times that are
permitted for application and release of brake chamber
pressure. Refer to Figure 2. ABS equipped trailers must
meet the same air timing requirements as prior, non-ABS
equippedtrailers.
Reservoirs
Trailers must be equipped with air reservoirs that provide
a volume of air eight times that of the service brake
chambers.
Forexample: atype30 airchamberhasan effectivesurface
area of 30 sq. in. For short stroke type 30 air chambers,
thevolumeistypically89 CID. For a typical two axle trailer,
the minimum required volume is therefore 2848 CID.
Reservoir size requirements for non-ABS and ABS
equipped systems are the same.
Air Consumption
DuringABSactivationthere is a loss of reservoir pressure.
Thereareno specific requirementslimitingairconsumption
in the U.S. (In Europe Regulation R13 states specific
limitations). ABS manufacturers take air consumption into
account when developing and evaluating ABS control
algorithms. There has been no need to change reservoir
size requirements as a result of theABS mandate.
Vehicle Classification Application Time (seconds) Release Time (seconds)
Tractors,Trailers and Buses .45 .35 .75 .55
Towing Trailer .50 .50 1.001.00
Converter Dolly .55 .55 1.101.10
Single Trailer .60 — 1.20 —
Note:A50 cubic inch reservoir is used to simulate the towed trailer volume at the gladhands of towing units.
From pedal
movement
for chambers
to reach 60 PSI
Pedal movement
to reach 60 PSI
at 50 cu. Res
at gladhand
From pedal
movement to
reach 5 PSI
(w/95 PSI initial
chamber pressure)
From movement
of the pedal until
50 cu. in. reservoir
reaches 5 PSI
(With 95 PSI initial
chamber pressure)

4
3/4"
Reservoir
Port
1/4"
Supply Port 1/4"
Control
Port
3/8"
Delivery
Ports
3/8"
Delivery Ports
TEV
3/4"
Reservoir
Port
1/4" Supply Port
1/4"
Control
Port
3/8"
Delivery
Ports
3/8"
Delivery Ports
STEV
FIGURE 3 - Spring Brake Control Valves
Brake Priority Options
In prior years, there were requirements for a protected
reservoir, separate from the main reservoir. The purpose
of the protected reservoir was to hold off the spring brakes
in the event of a failure of the service brake system.
In1994,FMVSS-121was revisedtoallowotherapproaches
to reservoir management. The protected reservoir
approach, although not required, is still acceptable.
Conventional trailers are designed for either:
• Spring Brake Priority or
• Service Brake Priority.
Spring Brake Priority–The advantage of spring brake
priority is that the parking brakes (spring brake) can be
released quickly to permit moving the trailer at start up.
However, spring brake priority systems have failure modes
under which the parking brakes can be released and the
vehicle operated without functional service brakes.
ServiceBrake Priority–Theadvantageof theservicebrake
priority system is that it assures that the service brakes
haveadequateairpressure availabletothembeforerelease
of the spring brakes is allowed. However, service brake
priority systems require more time to bring a vehicle up to
operationallevel.
The Bendix®A-18™trailer ABS system is compatible with
both Spring Brake Priority and Service Brake Priority
systems and does not require special installation
procedures. A number of spring brake control valves are
suitable for meeting current requirements. Bendix offers
spring brake valves suitable for a range of applications.

5
Speed sensors
monitor wheel
rotation
Speed signal
to ECU
ECU interprets
speed signals
and activates valves
Hold and release solenoids
control air pressure in the
brake chambers
Braking force
remains at
optimum level
Res. 3
4
5
1
2
FIGURE 4 - Overview of Trailer ABS Operation
ABS PERFORMANCE CHARACTERISTICS
Routine Braking
During routine braking operations, there is no indication of
excessivewheel slip. The electronic controlunit interprets
this condition as normal andABS remains inactive.
ABS Controlled Braking
The control unit continuously monitors all available wheel
speedsensors. Datafromthesensorsis used to calculate
values of wheel speed and wheel slip and to make a best
estimate of the true vehicle speed. This data allows the
control unit to detect impending wheel lock and to hold the
wheel slip at an optimum value to maximize braking
effectiveness. Thebestpossiblevehiclestabilityisassured
while stopping distance is minimized.
Control is accomplished by operation of relay based
modulator valves. The control unit makes a new
assessment of conditions and updates the control signal
tothe modulator valvesatarate of approximately100times
per second.
Undernormal(non-ABS)conditions, trailerABSrelayvalves
operateexactly like conventional mechanicalrelay valves.
(Refer to Figures 11 through 14.) During ABS operation,
the control unit operates the valves to override the supply
of air to the chambers. During an ABS release, supply air
isheldoffwhilethe chambersarevented totheatmosphere.
Inholdmode, supply air is blocked and chamberairisheld
constant. When required, air is applied to the chamber at
a controlled rate by modulating the hold side of the valve.
The antilock system does not apply additional braking
power. Rather, it controls air pressure to release and hold
brake torque, thereby increasing a vehicle’s capacity for
quick,straightstops. WithABSinstalled,vehicle operation
is safer, resulting in improved protection of driver, cargo
and equipment.
ABS Component Function
Figure4showsanoverviewoftheoperationof the Bendix®
A-18™trailerABS system.
Speed sensors (1) monitor wheel rotation and provide
information (2) on wheel rotation to the central electronic
control unit.
The Electronic Control Unit (3) receives the sensor signal,
interprets the pulse information, and constantly calculates
the relationship of speed, acceleration, and deceleration.
Acontrolsignal (4) is sent to theABS relay valve(5),which
then controls the pressure to the air chambers.
System Designs
When operating on high traction surfaces with a loaded
vehicle, there is little difference between types of ABS
control. Performance differences appear when vehicles
arelightlyloadedandoperatingonvariableand poortraction
surfaces. Examples of poor traction surfaces are ice and
combinationsof ice, snow andasphalt. Operatingavehicle
inacurve highlightsdifferencesin stabilitybetween various
systems.
ABSsystemdesignsprovidecompromisesbetweenstability
and stopping distance while addressing cost, complexity
and reliability issues.

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Independent Regulation
The most obvious control concept is independent wheel
control. In this case a single sensor controls a valve that
operates the brakes at one wheel site. Individual control
makes the best trade off between stability and stopping
distance. However, these systemshavegreatercomplexity
and higher cost with potentially lower reliability than less
complexsystems. Inmany cases it is necessary to control
a single valve with inputs from two sensors.
Select Low
Select low systems monitor several wheels and controls
them with a single valve. Control is based on the wheel
that is at the lowest speed. Select low systems are very
stable but sacrifice stopping distance on split coefficient
surfaces. Modifiedselectlow systems incorporate a delay
before releasing to reduce the bias slightly away from the
low speed wheel.
Select High
Selecthighsystemsalso monitorseveralwheelsandcontrol
them with a single valve. Control is based on the wheel
whichis at the highestspeed. Modifiedselecthigh systems
activate a release before the low speed wheel becomes
severelylocked. Selecthighsystemsgenerallyhave good
stopping distances at the expense of stability. These
systemsmay alsohavean increasedriskoftire flatspotting.
Select Smart
SelectSmartsystemsoperateasselectlowsystemswhen
there is little difference in traction between wheel control
sites. Theyoperateasselecthighsystemswhenthereisa
significant difference in traction between sites. These
systems offer many of the advantages of individual control
systems while using a simpler design and fewer
components.
Bendix®A-18™Trailer ABS Control Strategy
Select Smart is used for the most common applications.
Select low is used on the standard system 4S/2M Axle
Control configuration and is available as an option on the
basic system.
TRAILERABS CONFIGURATIONS
Application Recommendations
Refer to the chart on page 8 to determine a recommended
ABS installation for your application.
Basic System (2S/1M)
The basic system includes two speed sensors and one
modulator valve for direct control of one axle and indirect
control of an additional axle. Other features of the basic
system include one ECU connector and a single-pin
diagnostic lead.
Standard System (2S/1M, 2S/2M and 4S/2M)
Bendix’s standard systems offer either two or four speed
sensorsand up totwomodulatorvalves. Standardsystems
can directly control one or two axles and allow full
diagnostics via J1587. The standard system may be
configured in one of four ways to function as follows:
• 2S/1M—This configuration uses two sensors and one
modulatorvalvetodirectly controloneaxleandindirectly
control an additional axle.
• 2S/2M—Thisconfiguration usestwospeed sensorsand
two modulator valves for direct control of one axle and
indirect control of up to three additional axles.
• 4S/2M—This configuration uses four speed sensors
andtwomodulatorvalves for direct control of two axles
and indirect control of up to two additional axles.
• 4S/2M Axle Control—Special configuration for full
trailers and widely spaced axles. This configuration
uses the select low strategy.
Sensor Placement
When more than one wheel is controlled by a single valve,
sensorsshould be mounted at the axlewhichtends to lock
first. For spring suspensions this is usually the forward
axle. Forairsuspensionsthisisusuallytherearmostaxle.
Lift Axles
• Gen-4™ABS: Sensor inputs “C” and “D” of the control
unit may be used for lift axle wheel speed sensing.
• Gen-5™ABS:Direct liftaxle control isnotavailable. Use
indirect control.
Reading Configuration Codes
On Basic systems, the jumper method must be used to
access the configuration. On Standard systems, access
to configuration information can be achieved by any of the
three methods:
• ServiceRanger diagnostic software on a PC
• Hand-held tester
• Jumper method.
For more information on accessing configuration codes,
refer toAccessing Codes on page 30.

7
Semi
Trailer
or
1st
Trailer
1st
2nd
or
3rd
Trailer
Trailer
Dolly
SystemApplication Chart
(1) (1)
(1) (1) (1)
(1)
(1)(1)
(1)
(1)
(2)
(2)
(2)
(2)
(1) (1)
(1) (1)
(1) (1) (1)
(1) (1)
(1)
(2)
(1)
(1)
(1)
or
or or
(2)
or
(2)
or
(2)
(1)(2)
or
orand
(1)(2) and
(2)
or
(1)
or
(2)
or
(1)
or
or or
or
or
or
or
2S/1M 2S/2M 4S/2MAxle Control
4S/2M Side Control
Trailer Type
FIGURE 5 - System Application Chart

8
Trailer ABS Component Overview
Bendix®A-18™trailer ABS system includes the following
components:
•Electronic Control Unit (ECU): The ECU monitors
wheel speeds and controls the trailer ABS valves. It
also diagnoses ABS malfunctions and stores failure-
specific fault codes. The ECU is usually attached to a
relay valve with a mounting bracket. The ECU may
alsobedirectly frame mounted. One ECU can monitor
eithertwo or four speed sensors andcontrol either one
or two relay valves. If necessary more than one ECU
may be used on a single trailer.
•Relay Valve: This component regulatesbrakechamber
airpressure. Ithouses the hold and release solenoids.
Each relay valve can control either two or four brake
chambers on an ABS equipped trailer. A relay valve
can have the ECU mounted to it (valve A in the
installation diagrams) or be a stand alone relay valve
(valve B in the installation diagrams) that is controlled
remotely by the ECU mounted on valveA.
•Trailer Mounted ABS Warning Lamp: This indicator
lamp, located on the “Road Side” near the rear of the
trailer, warns the driver of ABS malfunctions (steady
“ON”). It is also capable of blinking diagnostic fault
codes.
•Cab Mounted ABS Warning Lamp: This indicator
lamp,located on thedriverinstrumentpanel,alsowarns
the driver of ABS malfunctions. It is not capable of
blinking diagnostic fault codes.
•Wheel End Speed Sensor and Tone Wheel: Single
point variable reluctance (magnetic) sensor that
generates an alternating current signal in response to
the movement of teeth on a tone wheel. The signal is
interpreted by the ECU to monitor wheel speed.
•Diagnostic Port Connector: The diagnostic port
connector is an industry standard connector which is
used to provide a connection to the J1587 diagnostic
link. This connector also provides power and ground
for diagnostic test equipment.
•Gladhand: The gladhands used on the ABS system
are the same as those used on non-ABS trailers.
•Seven Way Main Electrical Connector: The seven
wayreceptacleis the same as those used on non-ABS
systems. This receptacle provides full-time power,
backup power via the brake light switch and ground for
theABS electrical system.
•Optional ISO 3731 connector: This is a 7-pin
connector similar to the J560 connector. The most
noticeable difference is that the ground terminal has a
genderopposite thatoftheother terminals. Theprimary
use for ISO 3731 is for the lighting connections on
European trailers. However, this connector is used to
provide interface to trailer ABS in some U.S.
applications. (InEuropeanotherconnectordesignated
as ISO 7638 is used to provide interface to the trailer
braking system.)

9
FIGURE 6 - ABS Trailer Components

10
ECU Cover
Relay Valve
BASIC STANDARD
ECU Cover
Plug Blank
Connector
Relay Valve
FIGURE 8 - Trailer ABS ECU Configurations
FIGURE 7 - Electronic Control Unit Identification Tags
Electronic Control Unit (ECU)
The Bendix®A-18™ECU is the trailerABS control center.
Identification
Identification information for the ECU is located on the
connector pinout label (refer to Figure 7). The label is
located under the ECU cover. Refer to the label for the:
• Part Number
• Serial Number
• Date Code.
Depending on configuration, theA-18™trailerABS system
ECUs may be equipped with either one connector (basic
system) or two connectors (standard system). Refer to
Figure 8.
Bendix Part Number
Basic System
Serial Number Date Code
Standard System
Serial Number Date Code

11
FIGURE 9 - Standard and Basic ECU Block Diagrams
J1587
Diagnostic Link
Diagnostic
Switch
J1587+
J1587 Gnd
Release
Outputs
Trailer Mounted
Warning Light
X1-10
X1-12
X2-11
X2-12
X1-9
Inputs
Brake Light Power
Full Time Power
X1-5
SensorA
Sensor B
Sensor C
Sensor D
X2-6
X2-4
X2-8
ValveA
Valve B
X2-10
X1-7 X2-2
X2-1
Standard
Trailer
ECU
(2 Connectors)
+
+
X2-3
X2-5
X2-7
X2-9
X1-6
-
-
+
-
+
-
X1-4
X1-3
Hold
Common
X1-2
X1-1
Common
Hold
Release
Outputs
Trailer Mounted
Warning Light
Diagnostic Plug
X1-10
X1-8
X1-9
Inputs
Brake Light Power
Full Time Power
X1-5
SensorA
Sensor B X1-12
X1-1 ValveA
X1-7
Basic
Trailer
ECU
(1 Connector)
+
+
X1-2
X1-11
X1-6
-
-
X1-4
X1-3
Hold
Common

12
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
ThetrailerABSrelayvalvecontrolsairpressuretoindividual
brake assemblies, and functions as a standard relay valve
when there are noABS control signals. Depending on the
particular ABS configuration, a system may utilize one or
two relay valves. See Figure 10.
Eachrelayvalve containstwosolenoidsfor 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.
Eachrelay valve has a three-pin terminalfor 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. Usecaretomaintaincleanlinessofvalveinterior.
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
reorientingportsorwhenattaching fittings. If aviseisused,
thereisa potential dangerofdistortingthebarrel 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 INJURYOR 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
enginebe 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. Useonly the proper toolsand 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™airdryer systemor a dryer reservoir module,
be sure to drain the purge reservoir.
5. Following the vehicle manufacturer’s
recommendedprocedures, deactivate theelectrical
system in a manner that safely removes all
electrical power from the vehicle.

13
FIGURE 13 - ABS Hold
FIGURE 11 - Normal Apply and ABS Apply
FIGURE 14 - ABS Release
FIGURE 12 - Normal Release
Supply
Outlet Exhaust
Control
Supply
Outlet Exhaust
Control
Supply
Outlet Exhaust
Control
Supply
Release
Solenoid
Outlet
Sleeve
Piston
Control
Hold
Solenoid
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.
Relay Valve Operation Modes
1. Apply–Treadle pressure is applied to the top of the
piston. Thesleeve isdepresseduntil theoutletpressure
matches the pressure at the top of the piston.
2. Normal Release–Pressure at the top of the piston is
vented through the treadle valve. The sleeve rises to
blocktheinlet while allowing thechamberairtoexhaust
through the center of the sleeve.
3. ABS Hold–Holdsolenoidblockstreadlepressure. The
piston stabilizes, holding the chamber pressure at the
same level as that which is above the piston.
4. ABS Release–Thereleasesolenoidventsair atthetop
ofthepistonwhile blockingtreadlepressure. Thesleeve
risestoblockthe inlet while allowing the chamber air to
exhaust through the center of the sleeve.

14
FIGURE 15 - Speed Sensor Installation
Friction Sleeve
Sensor
ABS
Sensor
Bushing
Sensor
Push
FIGURE 16 - Wheel Speed Sensor Components
Installation
InstallationoftheBendix®A-18™trailerABSsystemissimilar
fromone configurationtoanother. All systemsusethesame
speed sensors and valves. The differences are in
placementandquantityandthetype ofECU,eitherstandard
or basic. Refer to the following general component
instructions and to the wiring and plumbing diagrams for
specific system configuration.
Suggested Order Of Installation
Following is a suggested order of installation of theA-18™
trailerABS.
1. Install Wheel Speed Sensors (often part of a dressed
axle).
2. Install Relay Valve(s)/ECU assembly.
3. Install the Power Cable, but do not apply power until
the installation is complete.
4. Route and connect the main ABS Harness.
5. Install the Diagnostic Port Connector.
6. Install the trailer-mountedABS Warning Lamp.
7. Perform the End-of-Line Checkout.
Install the Wheel Speed Sensors and Sensor
Friction Sleeves
Referto the appropriatediagramforyour systemandlocate
the wheel speed sensors. Refer to Figures 23-26.
1. Install the sensor friction sleeve with the flange stops
towards the inboard side of the vehicle.
2. Apply high-temperature silicon-based grease to the
body of the speed sensor.
3. Push the speed sensor completely into sensor friction
sleeve by hand until it stops against the tone ring. The
speedsensorisproperlyinstalledand adjusted when it
is touching the tone ring. Allowable TIR for the tone
ring is 0.008 inches.
NOTE: The speed sensor must be able to slide freely in
and out of the sensor friction sleeve bore. Operating the
vehicle with seized components will damage the speed
sensor and the tone ring.
4. Route the cabletotheframe. Usetiewraps as required
torestraincable. Usecare not to stress sensor cables.
5. Connect sensor cable to harness and install fasteners
to hold the sensor cable in position.

15
FIGURE 17- Tank Mounted ECU/Relay Valve
ECU
Relay Valve
3/4" Heavy Wall
Steel Pipe Nipple
Reservoir Tank
FIGURE 18 - Frame Mounted Relay Valve
ECU
Relay Valve
Frame
Member
Install the ECU/Relay Valve and Stand Alone
Relay Valve
Inallinstallations,the ECU/Relay Valve assembly appears
asRelayValve“A”inthediagrams. TheStandAloneRelay
Valve is identical to the ECU/Relay Valve except it does
not have the ECU and ECU mounting bracket. The relay
valves may be installed on the reservoirs or a frame
member.
The Stand Alone Relay Valve is the second relay valve in
systems with two relay valves and is labeled Relay Valve
“B” in the diagrams.
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
Leak and Performance Test
1. Park vehicle on level surface and block wheels.
2. Make and hold brake application. No audible air leaks
are permitted.
3. Release parking brake and fully charge the air system
(governor cut out point).
4. Turnengine OFF. Applytheservicebrakeseveraltimes,
then hold and check for prompt brake air chamber
application and release at all wheels.
5. Apply brake, then hold. Coat outsideofrelayvalvewith
a soap solution. No leakage is permitted.
NOTE: Ifa sluggishresponseisnoted atallwheels,inspect
for kinked or obstructed air line leading to or from valve.
6. Increase system air pressure to governor cut-off. With
brakesreleased,coatexhaustportofrelay valve with a
soap solution. Leakage of a 1” bubble in 5 seconds is
permissible.
7. Depress foot valve and keep depressed. Coat exhaust
port with a soap solution. Leakage of a 1” bubble in 3
seconds is permissible.

16
To
ECU/
Modulator
Valve
Power
Cable
ECU Side
Trailer
Side
To
Nose
Box
FIGURE 19 - Inline Power Connector
ABS ABS
5 Pin
Weatherpack
One Bayonett Connector
at Relay Valve
Diagnostic
Male
Bayonet
Warning
Light
Chassis
Ground
J560
6" Pigtail
Two
Speed
Sensors
Road SideRoad Side
5 Pin
Weatherpack
Deutsch
Hd-10
Diagnostic
Bayonett Connector
at Relay Valve
(Up to 2)
Male
Bayonet
Warning
Light
Chassis
Ground
J560
6" Pigtail
Speed
Sensor
(2 or 4)
BASICSTANDARD
FIGURE 20 - Standard and Basic ABS Harnesses
Install the Inline Power Connector
The inline power connector is on the end of the mainABS
harness and connects the ABS system to the trailer
electrical system.
Install the Main ABS Harness
1. Remove power from the trailer.
2. Unlock the ECU cover and remove.
3. Install the ECU connectors as follows:
Standard: Plug the grey harness connector into the
ECU connector labeled “X1”. The connector is keyed
andcanonlyfitinonedirection. Plug the black harness
connector into the ECU connector labeled “X2”. This
connector is also keyed.
Basic: Plugthe green harness connector into the ECU
connector labeled “X1”. This connector is also keyed
and is the only connector on the ECU.
4. Install the ECU cover by first engaging the alignment
tabs and then hinging the cover closed, ensuring that
theconvoluted tubingiscaptured inthestrain reliefslots.
Slide the cover lock to the locked position. An optional
tie wrap may be used to lock the cover in place.
5. Route harness to designated locations. Make sure that
the harness is properly routed and secured to prevent
damage to the harness.

17
Diagnostic
Port
To Frame
Diagnostic
Port Bracket
FIGURE 21 - Diagnostic Port Installation (Standard)
ABS
23.6"
(600mm)
5.9"
(160mm)
Rear
of
Trailer
Rear
Side Marker
ABS
Warning
Lamp
FIGURE 22 - Warning Light Location
Install the Diagnostic Port (Standard System)
On standard systems, the diagnostic port is installed on
the road side of the trailer, on the frame forward of the
trailer axle(s). To install the diagnostics port, bolt or weld
the diagnostic port bracket to the trailer frame.
Install the Trailer Mounted Warning Light
Thewarninglight is mounted on the road side of thetrailer,
forward of the marker light according to the following
drawing.

18
Gladhand
Gladhand
TEV or STEV
Spring Brake
Control
Res. Res.
Emergency
Brake
Chamber
Service
Brake
Chamber
ABS
ECU
3/4" Heavy Wall
Steel Pipe Nipple
Supply Line
Service (Control) Line
Front ABS
Relay
Valve
3/8" O. D. Nylon Tubing
3/8" O. D. Nylon Tubing (Alt. 1/2" O. D.)
3/8" I. D. Hose
Key
Road Side
Top View
Road Side
Top View
ECU
Side Wheel
Side
Power Cable
2S-1M Electrical Configuration (Top View)
J560 Connector
Trailer
Side
Warning
Light Side
Harness Side
ECU Side
Warning Lamp Connector ABS Warning LampECU
Modulator
Valve
Diagnostic Port Wheel Sensor Speed Sensor
Sensor B
SensorA
Front
ABS
2S-1MAir System Configuration (Top View)
(Shown with
Extension)
Description Quantity
ECU/Relay Valve 1
Sensor/Diagnostics Cable 1
Valve/Power Cable 1
Sensors — 0.4m Cable 2
Sensor Friction Sleeve 2
Parts List
FIGURE 23 - Typical 2S-1M ABS Electrical and Air System

19
Front
3/8" O. D. Nylon Tubing
3/8" O. D. Nylon Tubing (Alt. 1/2" O. D.)
3/8" I. D. Hose
Key
2S-2MAir System Configuration (Top View)
Gladhand
Gladhand
TEV or STEV
Spring Brake Control
Res. Res.
Emergency Brake Chamber
Service Brake Chamber
ABS
ECU
Relay Valve A
Relay
Valve
B
Supply Line
Service (Control) Line
Power Cable
2S-2M Electrical Configuration (Top View)
J560 Connector
Trailer
Side
ABS Warning LampECU
Relay
ValveA
Diagnostic Port Wheel Sensor Speed Sensor
Sensor B
SensorA
Front
ABS
Stand
Alone
Relay
Valve B
ECU
Side Wheel
Side
Warning
Light Side
Harness Side
Warning Lamp Connector
ECU Side
Road Side
Top View
Road Side
Top View
Description Quantity
ECU/Relay Valve 1
StandAlone Relay Valve 1
Sensor/Diagnostic Cable 1
Valve/Power Cable 1
Sensors — 0.4m Cable 2
Sensor Friction Sleeve 2
Parts List
FIGURE 24 - Typical 2S-2M ABS Electrical and Air System

20
Front
3/8" O. D. Nylon Tubing
3/8" O. D. Nylon Tubing (Alt. 1/2" O. D.)
3/8" I. D. Hose
Key
4S-2M Side ControlAir System Configuration (Top View)
Gladhand
Gladhand
TEV or STEV
Spring Brake Control
Res. Res.
Emergency Brake Chamber
Service Brake Chamber
ABS
ECU
Relay ValveA
Relay
Valve
B
Supply Line
Service (Control) Line
Road Side
Top View
Road Side
Top View
Power Cable
4S-2M Side Control Electrical Configuration (Top View)
J560 Connector
Trailer
Side
ABS Warning LampECU
Relay
ValveA
Stand
Alone
Relay
Valve B
Diagnostic Port Speed Sensor
Sensor D
Sensor C
SensorA
Sensor B
Front
ABS
ECU Side
Description Quantity
ECU/Relay Valve 1
StandAlone Relay Valve 1
Sensor/Diagnostic Cable 1
Valve/Power Cable 1
Sensors — 0.4m Cable 4
Sensor Friction Sleeve 4
Parts List
Wheel Sensor
ECU
Side Wheel
Side
Warning
Light Side
Harness Side
Warning Lamp Connector
FIGURE 25 - Typical 4S-2M Side Control ABS Electrical and Air System (Top View)