BENDIX ET-S SUSPENDED ELECTRON TREADLE User manual

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®
SD-15-4111
MOUNTING
PLATE
FIGURE 3 - OUTPUT VOLTAGE
OPEN THROTTLE
(FULL)
○○○○○○○○○○○○○○○○○○○○○○
0V
ET-S™
TREADLE
OUTPUT
VOLTAGE
ENGINE
MAX
RPM
IDLE
CLOSED THROTTLE
(OPEN)
MOUNTING
PLATE
POTENTIOMETER
CONNECTOR
FIGURE 1 - ET-S™AND ET-S2™ELECTRONIC TREADLES
CATERPILLAR
5V
8V
CUMMINS DETROIT
DIESEL
DESCRIPTION
The ET-S™and ET-S2™treadles are engine compartment
bulkhead mounted electronic treadles. On electronically
controlled diesel engines, the electronic treadle fulfills the
same function as a conventional mechanical throttle.
However, ratherthantransmittinga mechanicalforce tothe
enginegovernor,theelectronictreadlecontrolsenginespeed
by supplying a variable electrical voltage to the engine’s
electroniccontroller.
The main components of the ET-S™and ET-S2™treadles
are: a mounting plate, suspended treadle, potentiometer
(variable resistor), actuator body and base. The selected
potentiometer, chosen for a specific engine application,
provides the electrical link to the engine control system.
OPERATION
Theelectronictreadles providesmooth,graduated throttle
control through the function of its potentiometer (variable
resistor). The drive shaft of the cam follower assembly
transfers anymovementofthetreadle tothepotentiometer.
ACTUATOR BASE
TREADLE
TREADLE
Bendix®ET- S™& ET-S2™Suspended Electronic Treadle
ACTUATOR BODY
DETROIT CATERPILLAR CUMMINS
DIESEL
CLOSED
THROTTLE 7 - 18% 10 - 20% 5 - 17%
IDLE (OPEN)
OPEN
THROTTLE 74 - 90% 75 - 90% 70 - 81%
(FULL)
FIGURE 2 - OUTPUT VOLTAGE, AS A PERCENTAGE OF
SUPPLY VOLTAGE
ET-S2™TREADLE
TREADLE
TREADLE PIVOT PIN
MOUNTING
PLATE
POTENTIOMETER
ET-S™TREADLE

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As the driver depresses the treadle, the electronic treadle
outputvoltage increases(seeFigure3). Thepotentiometer
allowsanincreasedamountof itssupplyvoltagetoreturn to
theengine controlunit, whichin turnincreases theengine’s
speed.
In the full, or “Open Throttle” position, the driver has
depressed the treadle to its furthest possible point. This is
the state of least potentiometer resistance. The electronic
treadlereturns the maximumpercentage of supplyvoltage
to the engine control unit (see Figure 2).
PREVENTIVE MAINTENANCE
Important: Review the warranty policy before performing
anyintrusivemaintenanceprocedures.Anextendedwarranty
maybe voidedif intrusivemaintenance isperformed during
thisperiod.
Becausenotwo vehiclesoperateunder identicalconditions,
maintenanceintervalswillvary.Experienceisavaluableguide
indetermining thebestmaintenance intervalfor avehicle.
GENERAL
Important: Visually check for physical damage to the
electronictreadle suchas brokenormissing parts. Actuate
thepedal fivetimesfrom stopto stop, notingany bindingor
softpedal response.
ImportantNote:DONOTDISASSEMBLETHEACTUATOR
BODY. Replace the ET-S™or ET-S2™treadle if there is
any binding, soft pedal actuation or if the nylon washers or
retaining rings indicated in Figure 4 are cracked or have
signsof deterioration.
Performtheinspectionspresented attheprescribedinterval.
Iftheelectronictreadlefailstofunctionasdescribed,itshould
berepairedorreplacedwithaneworgenuineBendixremanu-
facturedunit,availableatanyauthorizedpartsoutlet.
Every3months, or 25,000miles, or900operatinghours:
1. Remove any accumulated contaminants and visually
inspect the exterior of the electronic treadle assembly
forphysical damage orexcessive corrosion.
2. Inspect electrical connections and cable assembly for
signsof corrosion, wear,or physical damage. Replace
as necessary.
3. Inspect treadle spring, sleeve bearing, nylon washer,
rubbertreadle cover (ET-S™treadle only) andretaining
ring forcracksor deterioration. Replaceas necessary.
ET-S™& ET-S2™TREADLE REMOVAL
1. Parkthe vehicleonalevelsurfaceandblockthewheels.
2. Drainthe airpressure fromall vehiclereservoirs.
3. Disconnect the cable assembly of the potentiometer.
Lift the lock tab and pull the connectors until they
disengage.
4. Removetheelectronictreadlefromthevehicle, setaside
themounting hardwarefor reassembly.
DISASSEMBLY
PleasenotethattheinternalmechanismoftheET-S™and
ET-S2™treadle are not field-serviceable and therefore
individual parts or parts kits are not available for these
components.Disassembly mayleadtomalfunctionof the
ET-S™or ET-S2™treadle.
The following instructions cover the maintenance and
replacement of the potentiometer and treadle (with its
bearing, spring etc.) only. The instructions provided with
thoseitemsshould befollowedin lieuofthe stepspresented
here.There arenootherfield-serviceableparts.
As the potentiometer rotates, its resistance changes. This
way,thepotentiometer can react tothe driver’s requestfor
engine power through the ET-S™or ET-S2™treadle by
changing resistance. The resulting change of voltage is
sensedby the electronicenginecontroller.
The electronic treadle receives its supply voltage from the
engine control unit. If the driver does not request engine
power, the treadle is in the idle position. This condition is
also referred to as “Closed Throttle.” In this state, the
potentiometer returns the minimum percentage of supply
voltageto the enginecontrolunit (seeFigure2).
RETAINING
RINGS
MOUNTING PLATE
FIGURE 4 - TOP SECTIONAL VIEW
CAM FOLLOWER
DRIVE SHAFT
POTENTIOMETER
NYLON
WASHERS

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All other repairs require replacement of the ET-S™or
ET-S2™treadle.
Referto Figure5 throughouttheprocedures.
Treadle Removal:
ET-S™Treadle
Position the treadle on its side with the potentiometer fac-
ingup. Remove thesmall retainingring (3)and smallnylon
washer (4) that hold the treadle on to the treadle arm and
set aside for the assembly process. After the washer is
removed, pull the treadle off, carefully releasing the pres-
sure from the treadle spring (7). Set the spring (7), nyliner
bearing (6) and the treadle aside for the reassembly pro-
cess.Inspect rubber treadlecover- replaceifnecessary.
ET-S2™Treadle
Position the treadle assembly on its side with the poten-
tiometer facing down. Remove the small retaining ring (3)
andthe nylon washer(4) from thetreadle pivotpin.
Remove the pivot pin from the treadle assembly. Gently
releasethe tensionon thetreadle spring(7) whileremoving
thetreadle from thetreadle arm. Removethenyliner bear-
ing(6) from thetreadle arm.
Potentiometer Removal:
Secure the mounting plate. Important: Do not clamp the
assembly by the treadle actuator body or base since
overclamping may cause the casting to be distorted.
Remove the two screws (2) that secure the potentiometer
(1)to theactuator base. Thepotentiometer(1)canthen be
liftedaway fromthedrive shaft.
CLEANING AND INSPECTION
1. Use suitable solvent to clean all metal parts (note that
mineral spirits may damage the paint finish).
2. Inspect the treadle and mounting plate for severe
corrosion, pitting, or cracks. Replace as necessary.
Superficialcorrosion and/or pittingis acceptable.
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SPRING
PIVOT PIN
ACTUATOR
BODY
MOUNTING
PLATE
ACTUATOR
BASE 1
POTENTIOMETER
2
#10 SCREWS
3
RETAINING
RING
4
NYLON
WASHER
TREADLE
5
REPLACEABLE
RUBBER
COVER
(ET-S™TREADLE
ONLY)
6
NYLINER
BEARING
TREADLE
ARM
FIGURE 5 - ET-S™AND ET-S2™TREADLE EXPLODED LINE DRAWING
7
SPRING
3
RETAINING
RING
4
NYLON
WASHER
TREADLE
ET-S™TREADLE
ET-S2™
TREADLE
TREADLE
ARM
PIVOT PIN 6
NYLINER
BEARING

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FIGURE 6 - ELECTRICAL TEST SCHEMATIC FOR THE DETROIT DIESEL CONNECTOR
FIGURE 7 - ELECTRICAL TEST SCHEMATIC FOR THE CATERPILLAR CONNECTOR
POWER
SUPPLY
(9-16VDC)
300,000 OHM RESISTOR
TEST LOAD
DIGITAL
VOLT/
OHM
METER
PIN C
GROUND
PIN B
VOUT
(OUTPUT)
PIN A
VREF
(INPUT)
POTENTIOMETER
PC. NO. ON THIS SURFACE
POTENTIOMETER
Closed Throttle (open) Range: 7-18%
Open Throttle (full) Range: 74-84%
PEDAL
POSITION
SENSOR
(PWM)
.001µF (CABLE)
POSITIONSENSOR
47,000 OHM ±5%
RESISTOR
PIN C
GROUND
2000 OHM ±5%
RESISTOR
PIN A VREF
(INPUT)
PIN B
VOUT
(OUTPUT)
Closed Throttle (open) Range: 10-20%
Open Throttle (full) Range: 75-90%
Caterpillar output voltage is Pulse Width Modulated
3. Inspect the cable assembly for loose or frayed wires,
physical damage, or any contaminants on the connec-
tors. Replace as necessary.
ASSEMBLY
1. Securelyclamp thetreadlemountingplate.
2. (a) For Detroit Diesel Potentiometers:Alignthe drive
slot,and engagethe potentiometerthe drivetangat the
end of the drive shaft (see Figure 4). Rotate the
potentiometer clockwise until the first set of mounting
holesalign. Secure usingtwo screws:torque to25(±5)
in. lbs.
(b)For Caterpillar Position Sensor:Aligning thedrive
slot, the position sensor engages the drive tang at the
endof thedriveshaft (seeFigure 4). Rotatetheposition
sensor clockwise until the first set of mounting holes
align. Secure using two screws : torque to 20 (±2) in.
lbs.

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FIGURE 8 - ELECTRICAL TEST SCHEMATIC FOR THE CUMMINS CONNECTOR
(c)ForCummins Potentiometers:
Test 1: Where the set resistance and voltage is
shown on a label. The Cummins potentiometer on
the ET-S™and ET-S2™treadle has an integral idle
validation switch. It also has a set resistance value
markedonthe cover,which needstobeusedtoproperly
install the potentiometer. The drive slot in the
potentiometer should engage with the drive tang at the
end of the drive shaft. Next rotate the potentiometer
untilthe hole inthe metalsleevematches themounting
holes on the actuator base. Loosely screw the
potentiometer in place but do not tighten. Connect an
ohmmeter to pins 3 (APS output) and 4 (APS ground)
asshown inFigure8. Now theinstaller shouldread the
set resistance value marked on the label. Rotate the
potentiometer until the ohmmeter reads the same
resistanceasshownonthelabelwithin±10Ohms. Next,
while holding the potentiometer at the set resistance
screwand lock thepotentiometer in place(torque to 25
inch pounds ±5). The sleeves lock into the body of the
potentiometerfor easyremoval andreassembly.
Test 2: Where the potentiometer has no label, but
has engraved set voltage shown. The Cummins
potentiometer on the electronic treadle has an integral
idle validation switch. It also has a set voltage value
markedonthe cover,which needstobeusedtoproperly
install the potentiometer. The drive slot in the
potentiometer should engage with the drive tang at the
end of the drive shaft. Next rotate the potentiometer
untilthe hole inthe metalsleevematches themounting
holes on the actuator base. Loosely screw the
potentiometerin placebut donot tighten. Constructthe
testcircuit followingthecircuit diagramshown inFigure
8. Tomakethe testcircuit connectthe testload resistor
(47,000Ohms)andacapacitor(.01MicroFarads)across
pins 3 and 4 of the potentiometer. Then connect a
voltmetertotheleadendsofthetestcircuit. Nextconnect
a5 voltpower supplyto thepotentiometer atpin4(APS
ground) and pin 5 (supply voltage). Caution: Sensor
may be damaged if supply exceeds 5 volts. Now the
installer should read the set voltage value marked on
the potentiometer. Rotate the potentiometer until the
voltmeter reads the same voltage as shown on the
potentiometer within ±.02 volts. Next screw and lock
the potentiometer in place (torque to 25 inch pounds
±5). Thesleeveslockintothe bodyofthepotentiometer
foreasy removaland reassembly.
Test3: Perform thefollowing Operational Test before
installingtheelectronic treadle:
OPERATIONALTEST
[Note for Cummins potentiometers only: The optimum
output & switch points should be achieved when the idle
voltage equals the set voltage or set resistance written on
the potentiometer. Use the test circuit shown in Figure 8.]
a. Check that the electronic treadle mounting plate is
securely attached to a smooth, flat surface in such a
way that does not twist the unit.
.01µF
TEST LOAD
47000 OHM
IDLE
VALIDATION
SWITCH
IVS
PEDAL
POSITION
SENSOR
PIN 3
PIN 4
PIN 5 Vs
SUPPLY
VOLTAGE
V1
(OUTPUT)
APS
GROUND
PIN 2
PIN 6
PIN 1
TEST
LOAD
470
OHM
TEST
LOAD
470
OHM
Vs
SUPPLY
VOLTAGE
DIODES Closed Throttle (open) Range: 5-17%
Open Throttle (full) Range: 70-81%
V3 (LOGIC HIGH AT IDLE)
V2 (LOGIC LOW AT IDLE)
IVS GROUND
3
V1
(OUTPUT) SIG1 2
(IVS) V 2
1
IVS GROUND
6
(IVS)
V 3
5
VS
(INPUT)4
APS GROUND
POTENTIOMETER
SET VOLTAGE
AND PC. NO.
SHOWN
HERE
LOCK TAB
LOCK TAB

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b. Connectthe potentiometeror positionsensor tothe volt
meter and power supply as shown in Figures 6, 7 or 8,
dependingonthemodel. Note: Thepowersupplyneeds
to be 5 VDC. Do not exceed this voltage.
c. Verify that the closed throttle (idle) output voltage, as a
percentage of supply voltage, is within the limits listed
in Figure 2. For example, with a supply voltage of 5
volts,fortheCaterpillarpotentiometerinitsclosedthrottle
position, read between 0.5 to 1.0 volts (10%-20% of
suppliedvoltage).
d. Depressthe treadletoits fullthrottleposition. Theoutput
voltage, as a percentage of supply voltage, should be
within the limits listed in Figure 2. For example, with a
supply voltage of 5 volts, for the Caterpillar position
sensor in its open throttle position, read between 3.75
to4.5 volts(75-90% ofsuppliedvoltage).
e. Makefivefullapplicationsandrecordidlepositionvoltage
eachtime. Verify thatidle positionvoltages recordeddo
not vary by more than .4% (For example, for a 5 volt
supply, if there is any variation, the difference between
thehigh and lowreadings shouldnotexceed .02volts).
If the electronic treadle fails to function within its specified
ranges, it should be repaired or replaced with a new or
genuine Bendix remanufactured unit, available at any
authorizedparts outlet.
Treadle Installation:
ET-S™Treadle
1. Replacethe rubbertreadle coverifneeded.
2. Place the spring (7) on the treadle pivot pin.
3. Install the nyliner bearing(6) into thetreadle. Note: the
nylinerbearingcollar is placedonthe treadle armside.
Holding the spring in position, the treadle is then in-
stalled.Thenylonwasher(4)andretainingring(3)secure
the treadle into position.
4. MakesuretheET-S™treadle hasasmooth,even treadle
movement.
5. Install the ET-S™treadle on the vehicle (see ET-S™&
ET-S2™TreadleInstallation).
ET-S2™Treadle
1. Positionthe treadleassemblyonitsside withthe poten-
tiometerfacing up.
2. Insertthe nylinerbearing(6) intothe treadlearmwith the
collarup (towardpotentiometer side). Thenyliner bear-
ing(6) will protrudethrough the treadlearm providing a
guidefor thetreadlespring (7).
3. Placethetreadlespring(7)ontheprotrudingportionofthe
nylinerbearingwiththetangsofthetreadlespring(7)point-
ingtowardtheET-S2™treadlebody. Theshorttangshould
rest on the top side of the treadle arm. Align the treadle
armandtreadlespringwiththerecess intheundersideof
thetreadle.
4. Insert the pivot pin from the potentiometer side of the
ET-S2™treadle assembly through the treadle, treadle
arm,nyliner bearing (6)and spring(7). Secure with the
nylonwasher (4)andretaining ring(3).
5. Makesure theET-S2™treadlehas smooth,eventreadle
movement.
6. Install the ET-S2™treadle on the vehicle (see ET-S™&
ET-S2™TreadleInstallation).
ET-S™& ET-S2™TREADLE INSTALLATION
1. Using the mounting hardware set aside, install the
assembled electronic treadle on the vehicle. Torque to
between 85 and 110 lb. in.
2. Reconnect the cable connector by plugging it into the
potentiometer’sintegral connectorandpushinguntilthe
lock tab snaps into place.
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 theproper tools andobserve
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,makecertain to draintheairpressure 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
recommendedprocedures, deactivate theelectrical
system in a manner that safely removes all
electrical power from the vehicle.
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.

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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.

8BW1837 © 2004 Bendix Commercial Vehicle Systems LLC. All rights reserved. 6/2004 Printed in U.S.A.